diff --git a/py/builtin.c b/py/builtin.c
index d4b77d37a8..9986b90d3f 100644
--- a/py/builtin.c
+++ b/py/builtin.c
@@ -172,13 +172,40 @@ STATIC mp_obj_t mp_builtin_callable(mp_obj_t o_in) {
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_callable_obj, mp_builtin_callable);
 
 STATIC mp_obj_t mp_builtin_chr(mp_obj_t o_in) {
-    int ord = mp_obj_get_int(o_in);
+    #if MICROPY_PY_BUILTINS_STR_UNICODE
+    machine_int_t c = mp_obj_get_int(o_in);
+    char str[4];
+    int len = 0;
+    if (c < 0x80) {
+        *str = c; len = 1;
+    } else if (c < 0x800) {
+        str[0] = (c >> 6) | 0xC0;
+        str[1] = (c & 0x3F) | 0x80;
+        len = 2;
+    } else if (c < 0x10000) {
+        str[0] = (c >> 12) | 0xE0;
+        str[1] = ((c >> 6) & 0x3F) | 0x80;
+        str[2] = (c & 0x3F) | 0x80;
+        len = 3;
+    } else if (c < 0x110000) {
+        str[0] = (c >> 18) | 0xF0;
+        str[1] = ((c >> 12) & 0x3F) | 0x80;
+        str[2] = ((c >> 6) & 0x3F) | 0x80;
+        str[3] = (c & 0x3F) | 0x80;
+        len = 4;
+    } else {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "chr() arg not in range(0x110000)"));
+    }
+    return mp_obj_new_str(str, len, true);
+    #else
+    machine_int_t ord = mp_obj_get_int(o_in);
     if (0 <= ord && ord <= 0x10ffff) {
         char str[1] = {ord};
         return mp_obj_new_str(str, 1, true);
     } else {
         nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "chr() arg not in range(0x110000)"));
     }
+    #endif
 }
 
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_chr_obj, mp_builtin_chr);
@@ -344,13 +371,32 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_oct_obj, mp_builtin_oct);
 STATIC mp_obj_t mp_builtin_ord(mp_obj_t o_in) {
     uint len;
     const char *str = mp_obj_str_get_data(o_in, &len);
+    #if MICROPY_PY_BUILTINS_STR_UNICODE
+    uint charlen = unichar_charlen(str, len);
+    if (charlen == 1) {
+        if (MP_OBJ_IS_STR(o_in) && UTF8_IS_NONASCII(*str)) {
+            machine_int_t ord = *str++ & 0x7F;
+            for (machine_int_t mask = 0x40; ord & mask; mask >>= 1) {
+                ord &= ~mask;
+            }
+            while (UTF8_IS_CONT(*str)) {
+                ord = (ord << 6) | (*str++ & 0x3F);
+            }
+            return mp_obj_new_int(ord);
+        } else {
+            return mp_obj_new_int(((const byte*)str)[0]);
+        }
+    } else {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "ord() expected a character, but string of length %d found", charlen));
+    }
+    #else
     if (len == 1) {
         // don't sign extend when converting to ord
-        // TODO unicode
         return mp_obj_new_int(((const byte*)str)[0]);
     } else {
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "ord() expected a character, but string of length %d found", len));
     }
+    #endif
 }
 
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_ord_obj, mp_builtin_ord);
diff --git a/py/lexer.c b/py/lexer.c
index 5d1113fb30..8732d64362 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -502,19 +502,32 @@ STATIC void mp_lexer_next_token_into(mp_lexer_t *lex, mp_token_t *tok, bool firs
                             case 'v': c = 0x0b; break;
                             case 'f': c = 0x0c; break;
                             case 'r': c = 0x0d; break;
+                            case 'u':
+                            case 'U':
+                                if (is_bytes) {
+                                    // b'\u1234' == b'\\u1234'
+                                    vstr_add_char(&lex->vstr, '\\');
+                                    break;
+                                }
+                                // Otherwise fall through.
                             case 'x':
                             {
                                 uint num = 0;
-                                if (!get_hex(lex, 2, &num)) {
+                                if (!get_hex(lex, (c == 'x' ? 2 : c == 'u' ? 4 : 8), &num)) {
                                     // TODO error message
                                     assert(0);
                                 }
                                 c = num;
                                 break;
                             }
-                            case 'N': break; // TODO \N{name} only in strings
-                            case 'u': break; // TODO \uxxxx only in strings
-                            case 'U': break; // TODO \Uxxxxxxxx only in strings
+                            case 'N':
+                                // Supporting '\N{LATIN SMALL LETTER A}' == 'a' would require keeping the
+                                // entire Unicode name table in the core. As of Unicode 6.3.0, that's nearly
+                                // 3MB of text; even gzip-compressed and with minimal structure, it'll take
+                                // roughly half a meg of storage. This form of Unicode escape may be added
+                                // later on, but it's definitely not a priority right now. -- CJA 20140607
+                                assert(!"Unicode name escapes not supported");
+                                break;
                             default:
                                 if (c >= '0' && c <= '7') {
                                     // Octal sequence, 1-3 chars
@@ -533,7 +546,13 @@ STATIC void mp_lexer_next_token_into(mp_lexer_t *lex, mp_token_t *tok, bool firs
                         }
                     }
                     if (c != MP_LEXER_CHAR_EOF) {
-                        vstr_add_char(&lex->vstr, c);
+                        if (c < 0x110000 && !is_bytes) {
+                            vstr_add_char(&lex->vstr, c);
+                        } else if (c < 0x100 && is_bytes) {
+                            vstr_add_byte(&lex->vstr, c);
+                        } else {
+                            assert(!"TODO: Throw an error, invalid escape code probably");
+                        }
                     }
                 } else {
                     vstr_add_char(&lex->vstr, CUR_CHAR(lex));
diff --git a/py/misc.h b/py/misc.h
index 3f62e3198f..bf63ce1354 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -100,7 +100,9 @@ bool unichar_isupper(unichar c);
 bool unichar_islower(unichar c);
 unichar unichar_tolower(unichar c);
 unichar unichar_toupper(unichar c);
-#define unichar_charlen(s, bytelen) (bytelen)
+uint unichar_charlen(const char *str, uint len); // TODO this should return machine_uint_t
+#define UTF8_IS_NONASCII(ch) ((ch) & 0x80)
+#define UTF8_IS_CONT(ch) (((ch) & 0xC0) == 0x80)
 
 /** variable string *********************************************/
 
@@ -164,4 +166,18 @@ int DEBUG_printf(const char *fmt, ...);
 
 extern uint mp_verbose_flag;
 
+// This is useful for unicode handling. Some CPU archs has
+// special instructions for efficient implentation of this
+// function (e.g. CLZ on ARM).
+// NOTE: this function is unused at the moment
+#ifndef count_lead_ones
+static inline uint count_lead_ones(byte val) {
+    uint c = 0;
+    for (byte mask = 0x80; val & mask; mask >>= 1) {
+        c++;
+    }
+    return c;
+}
+#endif
+
 #endif // _INCLUDED_MINILIB_H
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 5b27b910e7..0dd84d1f81 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -249,6 +249,11 @@ typedef double mp_float_t;
 /*****************************************************************************/
 /* Fine control over Python builtins, classes, modules, etc                  */
 
+// Whether str object is proper unicode
+#ifndef MICROPY_PY_BUILTINS_STR_UNICODE
+#define MICROPY_PY_BUILTINS_STR_UNICODE (0)
+#endif
+
 // Whether to support bytearray object
 #ifndef MICROPY_PY_BUILTINS_BYTEARRAY
 #define MICROPY_PY_BUILTINS_BYTEARRAY (1)
diff --git a/py/obj.c b/py/obj.c
index 7e39c5a5cc..12d7898428 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -357,7 +357,12 @@ uint mp_get_index(const mp_obj_type_t *type, machine_uint_t len, mp_obj_t index,
 
 // may return MP_OBJ_NULL
 mp_obj_t mp_obj_len_maybe(mp_obj_t o_in) {
-    if (MP_OBJ_IS_STR(o_in) || MP_OBJ_IS_TYPE(o_in, &mp_type_bytes)) {
+    if (
+#if !MICROPY_PY_BUILTINS_STR_UNICODE
+        // It's simple - unicode is slow, non-unicode is fast
+        MP_OBJ_IS_STR(o_in) ||
+#endif
+        MP_OBJ_IS_TYPE(o_in, &mp_type_bytes)) {
         return MP_OBJ_NEW_SMALL_INT((machine_int_t)mp_obj_str_get_len(o_in));
     } else {
         mp_obj_type_t *type = mp_obj_get_type(o_in);
diff --git a/py/objstr.c b/py/objstr.c
index c84d7c900d..a4749369d7 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -32,6 +32,7 @@
 #include "mpconfig.h"
 #include "nlr.h"
 #include "misc.h"
+#include "unicode.h"
 #include "qstr.h"
 #include "obj.h"
 #include "runtime0.h"
@@ -43,16 +44,7 @@
 STATIC mp_obj_t str_modulo_format(mp_obj_t pattern, uint n_args, const mp_obj_t *args, mp_obj_t dict);
 const mp_obj_t mp_const_empty_bytes;
 
-// use this macro to extract the string hash
-#define GET_STR_HASH(str_obj_in, str_hash) uint str_hash; if (MP_OBJ_IS_QSTR(str_obj_in)) { str_hash = qstr_hash(MP_OBJ_QSTR_VALUE(str_obj_in)); } else { str_hash = ((mp_obj_str_t*)str_obj_in)->hash; }
-
-// use this macro to extract the string length
-#define GET_STR_LEN(str_obj_in, str_len) uint str_len; if (MP_OBJ_IS_QSTR(str_obj_in)) { str_len = qstr_len(MP_OBJ_QSTR_VALUE(str_obj_in)); } else { str_len = ((mp_obj_str_t*)str_obj_in)->len; }
-
-// use this macro to extract the string data and length
-#define GET_STR_DATA_LEN(str_obj_in, str_data, str_len) const byte *str_data; uint str_len; if (MP_OBJ_IS_QSTR(str_obj_in)) { str_data = qstr_data(MP_OBJ_QSTR_VALUE(str_obj_in), &str_len); } else { str_len = ((mp_obj_str_t*)str_obj_in)->len; str_data = ((mp_obj_str_t*)str_obj_in)->data; }
-
-STATIC mp_obj_t mp_obj_new_str_iterator(mp_obj_t str);
+mp_obj_t mp_obj_new_str_iterator(mp_obj_t str);
 STATIC mp_obj_t mp_obj_new_bytes_iterator(mp_obj_t str);
 STATIC NORETURN void bad_implicit_conversion(mp_obj_t self_in);
 STATIC NORETURN void arg_type_mixup();
@@ -259,7 +251,7 @@ STATIC const byte *find_subbytes(const byte *haystack, machine_uint_t hlen, cons
     return NULL;
 }
 
-STATIC mp_obj_t str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
+mp_obj_t mp_obj_str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
     GET_STR_DATA_LEN(lhs_in, lhs_data, lhs_len);
     mp_obj_type_t *lhs_type = mp_obj_get_type(lhs_in);
     mp_obj_type_t *rhs_type = mp_obj_get_type(rhs_in);
@@ -352,11 +344,14 @@ uncomparable:
     return MP_OBJ_NULL; // op not supported
 }
 
+#if !MICROPY_PY_BUILTINS_STR_UNICODE
+// objstrunicode defines own version
 const byte *str_index_to_ptr(const mp_obj_type_t *type, const byte *self_data, uint self_len,
                              mp_obj_t index, bool is_slice) {
     machine_uint_t index_val = mp_get_index(type, self_len, index, is_slice);
     return self_data + index_val;
 }
+#endif
 
 STATIC mp_obj_t str_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
     mp_obj_type_t *type = mp_obj_get_type(self_in);
@@ -571,7 +566,6 @@ STATIC mp_obj_t str_rsplit(uint n_args, const mp_obj_t *args) {
     return res;
 }
 
-
 STATIC mp_obj_t str_finder(uint n_args, const mp_obj_t *args, machine_int_t direction, bool is_index) {
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
     assert(2 <= n_args && n_args <= 4);
@@ -600,6 +594,11 @@ STATIC mp_obj_t str_finder(uint n_args, const mp_obj_t *args, machine_int_t dire
         }
     } else {
         // found
+        #if MICROPY_PY_BUILTINS_STR_UNICODE
+        if (self_type == &mp_type_str) {
+            return MP_OBJ_NEW_SMALL_INT(utf8_ptr_to_index(haystack, p));
+        }
+        #endif
         return MP_OBJ_NEW_SMALL_INT(p - haystack);
     }
 }
@@ -1449,7 +1448,7 @@ STATIC mp_obj_t str_count(uint n_args, const mp_obj_t *args) {
 
     // if needle_len is zero then we count each gap between characters as an occurrence
     if (needle_len == 0) {
-        return MP_OBJ_NEW_SMALL_INT(unichar_charlen((const char*)start, end - start) + 1);
+        return MP_OBJ_NEW_SMALL_INT((machine_uint_t)unichar_charlen((const char*)start, end - start) + 1);
     }
 
     // count the occurrences
@@ -1610,7 +1609,7 @@ STATIC mp_obj_t str_encode(uint n_args, const mp_obj_t *args) {
 }
 #endif
 
-STATIC machine_int_t str_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, int flags) {
+machine_int_t mp_obj_str_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, int flags) {
     if (flags == MP_BUFFER_READ) {
         GET_STR_DATA_LEN(self_in, str_data, str_len);
         bufinfo->buf = (void*)str_data;
@@ -1627,38 +1626,45 @@ STATIC machine_int_t str_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo,
 }
 
 #if MICROPY_CPYTHON_COMPAT
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(bytes_decode_obj, 1, 3, bytes_decode);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_encode_obj, 1, 3, str_encode);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(bytes_decode_obj, 1, 3, bytes_decode);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_encode_obj, 1, 3, str_encode);
 #endif
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_find_obj, 2, 4, str_find);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rfind_obj, 2, 4, str_rfind);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_index_obj, 2, 4, str_index);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rindex_obj, 2, 4, str_rindex);
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(str_join_obj, str_join);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_split_obj, 1, 3, str_split);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rsplit_obj, 1, 3, str_rsplit);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_startswith_obj, 2, 3, str_startswith);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_endswith_obj, 2, 3, str_endswith);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_strip_obj, 1, 2, str_strip);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_lstrip_obj, 1, 2, str_lstrip);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rstrip_obj, 1, 2, str_rstrip);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR(str_format_obj, 1, mp_obj_str_format);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_replace_obj, 3, 4, str_replace);
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_count_obj, 2, 4, str_count);
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(str_partition_obj, str_partition);
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(str_rpartition_obj, str_rpartition);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_lower_obj, str_lower);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_upper_obj, str_upper);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_isspace_obj, str_isspace);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_isalpha_obj, str_isalpha);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_isdigit_obj, str_isdigit);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_isupper_obj, str_isupper);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(str_islower_obj, str_islower);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_find_obj, 2, 4, str_find);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rfind_obj, 2, 4, str_rfind);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_index_obj, 2, 4, str_index);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rindex_obj, 2, 4, str_rindex);
+MP_DEFINE_CONST_FUN_OBJ_2(str_join_obj, str_join);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_split_obj, 1, 3, str_split);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rsplit_obj, 1, 3, str_rsplit);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_startswith_obj, 2, 3, str_startswith);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_endswith_obj, 2, 3, str_endswith);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_strip_obj, 1, 2, str_strip);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_lstrip_obj, 1, 2, str_lstrip);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rstrip_obj, 1, 2, str_rstrip);
+MP_DEFINE_CONST_FUN_OBJ_VAR(str_format_obj, 1, mp_obj_str_format);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_replace_obj, 3, 4, str_replace);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_count_obj, 2, 4, str_count);
+MP_DEFINE_CONST_FUN_OBJ_2(str_partition_obj, str_partition);
+MP_DEFINE_CONST_FUN_OBJ_2(str_rpartition_obj, str_rpartition);
+MP_DEFINE_CONST_FUN_OBJ_1(str_lower_obj, str_lower);
+MP_DEFINE_CONST_FUN_OBJ_1(str_upper_obj, str_upper);
+MP_DEFINE_CONST_FUN_OBJ_1(str_isspace_obj, str_isspace);
+MP_DEFINE_CONST_FUN_OBJ_1(str_isalpha_obj, str_isalpha);
+MP_DEFINE_CONST_FUN_OBJ_1(str_isdigit_obj, str_isdigit);
+MP_DEFINE_CONST_FUN_OBJ_1(str_isupper_obj, str_isupper);
+MP_DEFINE_CONST_FUN_OBJ_1(str_islower_obj, str_islower);
 
 STATIC const mp_map_elem_t str_locals_dict_table[] = {
 #if MICROPY_CPYTHON_COMPAT
     { MP_OBJ_NEW_QSTR(MP_QSTR_decode), (mp_obj_t)&bytes_decode_obj },
+    #if !MICROPY_PY_BUILTINS_STR_UNICODE
+    // If we have separate unicode type, then here we have methods only
+    // for bytes type, and it should not have encode() methods. Otherwise,
+    // we have non-compliant-but-practical bytestring type, which shares
+    // method table with bytes, so they both have encode() and decode()
+    // methods (which should do type checking at runtime).
     { MP_OBJ_NEW_QSTR(MP_QSTR_encode), (mp_obj_t)&str_encode_obj },
+    #endif
 #endif
     { MP_OBJ_NEW_QSTR(MP_QSTR_find), (mp_obj_t)&str_find_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_rfind), (mp_obj_t)&str_rfind_obj },
@@ -1688,17 +1694,19 @@ STATIC const mp_map_elem_t str_locals_dict_table[] = {
 
 STATIC MP_DEFINE_CONST_DICT(str_locals_dict, str_locals_dict_table);
 
+#if !MICROPY_PY_BUILTINS_STR_UNICODE
 const mp_obj_type_t mp_type_str = {
     { &mp_type_type },
     .name = MP_QSTR_str,
     .print = str_print,
     .make_new = str_make_new,
-    .binary_op = str_binary_op,
+    .binary_op = mp_obj_str_binary_op,
     .subscr = str_subscr,
     .getiter = mp_obj_new_str_iterator,
-    .buffer_p = { .get_buffer = str_get_buffer },
+    .buffer_p = { .get_buffer = mp_obj_str_get_buffer },
     .locals_dict = (mp_obj_t)&str_locals_dict,
 };
+#endif
 
 // Reuses most of methods from str
 const mp_obj_type_t mp_type_bytes = {
@@ -1706,10 +1714,10 @@ const mp_obj_type_t mp_type_bytes = {
     .name = MP_QSTR_bytes,
     .print = str_print,
     .make_new = bytes_make_new,
-    .binary_op = str_binary_op,
+    .binary_op = mp_obj_str_binary_op,
     .subscr = str_subscr,
     .getiter = mp_obj_new_bytes_iterator,
-    .buffer_p = { .get_buffer = str_get_buffer },
+    .buffer_p = { .get_buffer = mp_obj_str_get_buffer },
     .locals_dict = (mp_obj_t)&str_locals_dict,
 };
 
@@ -1866,6 +1874,7 @@ typedef struct _mp_obj_str_it_t {
     machine_uint_t cur;
 } mp_obj_str_it_t;
 
+#if !MICROPY_PY_BUILTINS_STR_UNICODE
 STATIC mp_obj_t str_it_iternext(mp_obj_t self_in) {
     mp_obj_str_it_t *self = self_in;
     GET_STR_DATA_LEN(self->str, str, len);
@@ -1885,6 +1894,15 @@ STATIC const mp_obj_type_t mp_type_str_it = {
     .iternext = str_it_iternext,
 };
 
+mp_obj_t mp_obj_new_str_iterator(mp_obj_t str) {
+    mp_obj_str_it_t *o = m_new_obj(mp_obj_str_it_t);
+    o->base.type = &mp_type_str_it;
+    o->str = str;
+    o->cur = 0;
+    return o;
+}
+#endif
+
 STATIC mp_obj_t bytes_it_iternext(mp_obj_t self_in) {
     mp_obj_str_it_t *self = self_in;
     GET_STR_DATA_LEN(self->str, str, len);
@@ -1904,14 +1922,6 @@ STATIC const mp_obj_type_t mp_type_bytes_it = {
     .iternext = bytes_it_iternext,
 };
 
-mp_obj_t mp_obj_new_str_iterator(mp_obj_t str) {
-    mp_obj_str_it_t *o = m_new_obj(mp_obj_str_it_t);
-    o->base.type = &mp_type_str_it;
-    o->str = str;
-    o->cur = 0;
-    return o;
-}
-
 mp_obj_t mp_obj_new_bytes_iterator(mp_obj_t str) {
     mp_obj_str_it_t *o = m_new_obj(mp_obj_str_it_t);
     o->base.type = &mp_type_bytes_it;
diff --git a/py/objstr.h b/py/objstr.h
index 5be137d36d..515890c6e1 100644
--- a/py/objstr.h
+++ b/py/objstr.h
@@ -35,5 +35,53 @@ typedef struct _mp_obj_str_t {
 
 #define MP_DEFINE_STR_OBJ(obj_name, str) mp_obj_str_t obj_name = {{&mp_type_str}, 0, sizeof(str) - 1, (const byte*)str};
 
+// use this macro to extract the string hash
+#define GET_STR_HASH(str_obj_in, str_hash) \
+    uint str_hash; if (MP_OBJ_IS_QSTR(str_obj_in)) \
+    { str_hash = qstr_hash(MP_OBJ_QSTR_VALUE(str_obj_in)); } else { str_hash = ((mp_obj_str_t*)str_obj_in)->hash; }
+
+// use this macro to extract the string length
+#define GET_STR_LEN(str_obj_in, str_len) \
+    uint str_len; if (MP_OBJ_IS_QSTR(str_obj_in)) \
+    { str_len = qstr_len(MP_OBJ_QSTR_VALUE(str_obj_in)); } else { str_len = ((mp_obj_str_t*)str_obj_in)->len; }
+
+// use this macro to extract the string data and length
+#define GET_STR_DATA_LEN(str_obj_in, str_data, str_len) \
+    const byte *str_data; uint str_len; if (MP_OBJ_IS_QSTR(str_obj_in)) \
+    { str_data = qstr_data(MP_OBJ_QSTR_VALUE(str_obj_in), &str_len); } \
+    else { str_len = ((mp_obj_str_t*)str_obj_in)->len; str_data = ((mp_obj_str_t*)str_obj_in)->data; }
+
 mp_obj_t mp_obj_str_format(uint n_args, const mp_obj_t *args);
 mp_obj_t mp_obj_new_str_of_type(const mp_obj_type_t *type, const byte* data, uint len);
+
+mp_obj_t mp_obj_str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in);
+machine_int_t mp_obj_str_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, int flags);
+
+const byte *str_index_to_ptr(const mp_obj_type_t *type, const byte *self_data, uint self_len,
+                             mp_obj_t index, bool is_slice);
+
+MP_DECLARE_CONST_FUN_OBJ(str_encode_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_find_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_rfind_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_index_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_rindex_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_join_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_split_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_rsplit_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_startswith_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_endswith_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_strip_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_lstrip_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_rstrip_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_format_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_replace_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_count_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_partition_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_rpartition_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_lower_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_upper_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_isspace_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_isalpha_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_isdigit_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_isupper_obj);
+MP_DECLARE_CONST_FUN_OBJ(str_islower_obj);
diff --git a/py/objstrunicode.c b/py/objstrunicode.c
new file mode 100644
index 0000000000..35cc73bd84
--- /dev/null
+++ b/py/objstrunicode.c
@@ -0,0 +1,359 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013, 2014 Damien P. George
+ * Copyright (c) 2014 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+
+#include "mpconfig.h"
+#include "nlr.h"
+#include "misc.h"
+#include "qstr.h"
+#include "obj.h"
+#include "runtime0.h"
+#include "runtime.h"
+#include "pfenv.h"
+#include "objstr.h"
+#include "objlist.h"
+
+#if MICROPY_PY_BUILTINS_STR_UNICODE
+
+STATIC mp_obj_t mp_obj_new_str_iterator(mp_obj_t str);
+
+/******************************************************************************/
+/* str                                                                        */
+
+STATIC void uni_print_quoted(void (*print)(void *env, const char *fmt, ...), void *env, const byte *str_data, uint str_len) {
+    // this escapes characters, but it will be very slow to print (calling print many times)
+    bool has_single_quote = false;
+    bool has_double_quote = false;
+    for (const byte *s = str_data, *top = str_data + str_len; !has_double_quote && s < top; s++) {
+        if (*s == '\'') {
+            has_single_quote = true;
+        } else if (*s == '"') {
+            has_double_quote = true;
+        }
+    }
+    int quote_char = '\'';
+    if (has_single_quote && !has_double_quote) {
+        quote_char = '"';
+    }
+    print(env, "%c", quote_char);
+    const byte *s = str_data, *top = str_data + str_len;
+    while (s < top) {
+        unichar ch;
+        ch = utf8_get_char(s);
+        s = utf8_next_char(s);
+        if (ch == quote_char) {
+            print(env, "\\%c", quote_char);
+        } else if (ch == '\\') {
+            print(env, "\\\\");
+        } else if (32 <= ch && ch <= 126) {
+            print(env, "%c", ch);
+        } else if (ch == '\n') {
+            print(env, "\\n");
+        } else if (ch == '\r') {
+            print(env, "\\r");
+        } else if (ch == '\t') {
+            print(env, "\\t");
+        } else if (ch < 0x100) {
+            print(env, "\\x%02x", ch);
+        } else if (ch < 0x10000) {
+            print(env, "\\u%04x", ch);
+        } else {
+            print(env, "\\U%08x", ch);
+        }
+    }
+    print(env, "%c", quote_char);
+}
+
+STATIC void uni_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    GET_STR_DATA_LEN(self_in, str_data, str_len);
+    if (kind == PRINT_STR) {
+        print(env, "%.*s", str_len, str_data);
+    } else {
+        uni_print_quoted(print, env, str_data, str_len);
+    }
+}
+
+STATIC mp_obj_t uni_unary_op(int op, mp_obj_t self_in) {
+    GET_STR_DATA_LEN(self_in, str_data, str_len);
+    switch (op) {
+        case MP_UNARY_OP_BOOL:
+            return MP_BOOL(str_len != 0);
+        case MP_UNARY_OP_LEN:
+            return MP_OBJ_NEW_SMALL_INT((machine_int_t)unichar_charlen((const char *)str_data, str_len));
+        default:
+            return MP_OBJ_NULL; // op not supported
+    }
+}
+
+STATIC mp_obj_t str_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+#if MICROPY_CPYTHON_COMPAT
+    if (n_kw != 0) {
+        mp_arg_error_unimpl_kw();
+    }
+#endif
+
+    switch (n_args) {
+        case 0:
+            return MP_OBJ_NEW_QSTR(MP_QSTR_);
+
+        case 1:
+        {
+            vstr_t *vstr = vstr_new();
+            mp_obj_print_helper((void (*)(void*, const char*, ...))vstr_printf, vstr, args[0], PRINT_STR);
+            mp_obj_t s = mp_obj_new_str(vstr->buf, vstr->len, false);
+            vstr_free(vstr);
+            return s;
+        }
+
+        case 2:
+        case 3:
+        {
+            // TODO: validate 2nd/3rd args
+            if (!MP_OBJ_IS_TYPE(args[0], &mp_type_bytes)) {
+                nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "bytes expected"));
+            }
+            GET_STR_DATA_LEN(args[0], str_data, str_len);
+            GET_STR_HASH(args[0], str_hash);
+            mp_obj_str_t *o = mp_obj_new_str_of_type(&mp_type_str, NULL, str_len);
+            o->data = str_data;
+            o->hash = str_hash;
+            return o;
+        }
+
+        default:
+            nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "str takes at most 3 arguments"));
+    }
+}
+
+// Convert an index into a pointer to its lead byte. Out of bounds indexing will raise IndexError or
+// be capped to the first/last character of the string, depending on is_slice.
+const byte *str_index_to_ptr(const mp_obj_type_t *type, const byte *self_data, uint self_len,
+                             mp_obj_t index, bool is_slice) {
+    machine_int_t i;
+    // Copied from mp_get_index; I don't want bounds checking, just give me
+    // the integer as-is. (I can't bounds-check without scanning the whole
+    // string; an out-of-bounds index will be caught in the loops below.)
+    if (MP_OBJ_IS_SMALL_INT(index)) {
+        i = MP_OBJ_SMALL_INT_VALUE(index);
+    } else if (!mp_obj_get_int_maybe(index, &i)) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "string indices must be integers, not %s", mp_obj_get_type_str(index)));
+    }
+    const byte *s, *top = self_data + self_len;
+    if (i < 0)
+    {
+        // Negative indexing is performed by counting from the end of the string.
+        for (s = top - 1; i; --s) {
+            if (s < self_data) {
+                if (is_slice) {
+                    return self_data;
+                }
+                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_IndexError, "string index out of range"));
+            }
+            if (!UTF8_IS_CONT(*s)) {
+                ++i;
+            }
+        }
+        ++s;
+    } else if (!i) {
+        return self_data; // Shortcut - str[0] is its base pointer
+    } else {
+        // Positive indexing, correspondingly, counts from the start of the string.
+        // It's assumed that negative indexing will generally be used with small
+        // absolute values (eg str[-1], not str[-1000000]), which means it'll be
+        // more efficient this way.
+        for (s = self_data; true; ++s) {
+            if (s >= top) {
+                if (is_slice) {
+                    return top;
+                }
+                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_IndexError, "string index out of range"));
+            }
+            while (UTF8_IS_CONT(*s)) {
+                ++s;
+            }
+            if (!i--) {
+                return s;
+            }
+        }
+    }
+    return s;
+}
+
+STATIC mp_obj_t str_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
+    mp_obj_type_t *type = mp_obj_get_type(self_in);
+    GET_STR_DATA_LEN(self_in, self_data, self_len);
+    if (value == MP_OBJ_SENTINEL) {
+        // load
+#if MICROPY_PY_BUILTINS_SLICE
+        if (MP_OBJ_IS_TYPE(index, &mp_type_slice)) {
+            mp_obj_t ostart, ostop, ostep;
+            mp_obj_slice_get(index, &ostart, &ostop, &ostep);
+            if (ostep != mp_const_none && ostep != MP_OBJ_NEW_SMALL_INT(1)) {
+                nlr_raise(mp_obj_new_exception_msg(&mp_type_NotImplementedError,
+                    "only slices with step=1 (aka None) are supported"));
+            }
+
+            if (type == &mp_type_bytes) {
+                machine_int_t start = 0, stop = self_len;
+                if (ostart != mp_const_none) {
+                    start = MP_OBJ_SMALL_INT_VALUE(ostart);
+                    if (start < 0) {
+                        start = self_len + start;
+                    }
+                }
+                if (ostop != mp_const_none) {
+                    stop = MP_OBJ_SMALL_INT_VALUE(ostop);
+                    if (stop < 0) {
+                        stop = self_len + stop;
+                    }
+                }
+                return mp_obj_new_str_of_type(type, self_data + start, stop - start);
+            }
+            const byte *pstart, *pstop;
+            if (ostart != mp_const_none) {
+                pstart = str_index_to_ptr(type, self_data, self_len, ostart, true);
+            } else {
+                pstart = self_data;
+            }
+            if (ostop != mp_const_none) {
+                // pstop will point just after the stop character. This depends on
+                // the \0 at the end of the string.
+                pstop = str_index_to_ptr(type, self_data, self_len, ostop, true);
+            } else {
+                pstop = self_data + self_len;
+            }
+            if (pstop < pstart) {
+                return MP_OBJ_NEW_QSTR(MP_QSTR_);
+            }
+            return mp_obj_new_str_of_type(type, (const byte *)pstart, pstop - pstart);
+        }
+#endif
+        if (type == &mp_type_bytes) {
+            uint index_val = mp_get_index(type, self_len, index, false);
+            return MP_OBJ_NEW_SMALL_INT((mp_small_int_t)self_data[index_val]);
+        }
+        const byte *s = str_index_to_ptr(type, self_data, self_len, index, false);
+        int len = 1;
+        if (UTF8_IS_NONASCII(*s)) {
+            // Count the number of 1 bits (after the first)
+            for (char mask = 0x40; *s & mask; mask >>= 1) {
+                ++len;
+            }
+        }
+        return mp_obj_new_str((const char*)s, len, true); // This will create a one-character string
+    } else {
+        return MP_OBJ_NULL; // op not supported
+    }
+}
+
+STATIC const mp_map_elem_t str_locals_dict_table[] = {
+#if MICROPY_CPYTHON_COMPAT
+    { MP_OBJ_NEW_QSTR(MP_QSTR_encode), (mp_obj_t)&str_encode_obj },
+#endif
+    { MP_OBJ_NEW_QSTR(MP_QSTR_find), (mp_obj_t)&str_find_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_rfind), (mp_obj_t)&str_rfind_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_index), (mp_obj_t)&str_index_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_rindex), (mp_obj_t)&str_rindex_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_join), (mp_obj_t)&str_join_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_split), (mp_obj_t)&str_split_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_rsplit), (mp_obj_t)&str_rsplit_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_startswith), (mp_obj_t)&str_startswith_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_endswith), (mp_obj_t)&str_endswith_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_strip), (mp_obj_t)&str_strip_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_lstrip), (mp_obj_t)&str_lstrip_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_rstrip), (mp_obj_t)&str_rstrip_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_format), (mp_obj_t)&str_format_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_replace), (mp_obj_t)&str_replace_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_count), (mp_obj_t)&str_count_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_partition), (mp_obj_t)&str_partition_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_rpartition), (mp_obj_t)&str_rpartition_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_lower), (mp_obj_t)&str_lower_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_upper), (mp_obj_t)&str_upper_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_isspace), (mp_obj_t)&str_isspace_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_isalpha), (mp_obj_t)&str_isalpha_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_isdigit), (mp_obj_t)&str_isdigit_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_isupper), (mp_obj_t)&str_isupper_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_islower), (mp_obj_t)&str_islower_obj },
+};
+
+STATIC MP_DEFINE_CONST_DICT(str_locals_dict, str_locals_dict_table);
+
+const mp_obj_type_t mp_type_str = {
+    { &mp_type_type },
+    .name = MP_QSTR_str,
+    .print = uni_print,
+    .make_new = str_make_new,
+    .unary_op = uni_unary_op,
+    .binary_op = mp_obj_str_binary_op,
+    .subscr = str_subscr,
+    .getiter = mp_obj_new_str_iterator,
+    .buffer_p = { .get_buffer = mp_obj_str_get_buffer },
+    .locals_dict = (mp_obj_t)&str_locals_dict,
+};
+
+/******************************************************************************/
+/* str iterator                                                               */
+
+typedef struct _mp_obj_str_it_t {
+    mp_obj_base_t base;
+    mp_obj_t str;
+    machine_uint_t cur;
+} mp_obj_str_it_t;
+
+STATIC mp_obj_t str_it_iternext(mp_obj_t self_in) {
+    mp_obj_str_it_t *self = self_in;
+    GET_STR_DATA_LEN(self->str, str, len);
+    if (self->cur < len) {
+        const byte *cur = str + self->cur;
+        const byte *end = utf8_next_char(str + self->cur);
+        mp_obj_t o_out = mp_obj_new_str((const char*)cur, end - cur, true);
+        self->cur += end - cur;
+        return o_out;
+    } else {
+        return MP_OBJ_STOP_ITERATION;
+    }
+}
+
+STATIC const mp_obj_type_t mp_type_str_it = {
+    { &mp_type_type },
+    .name = MP_QSTR_iterator,
+    .getiter = mp_identity,
+    .iternext = str_it_iternext,
+};
+
+mp_obj_t mp_obj_new_str_iterator(mp_obj_t str) {
+    mp_obj_str_it_t *o = m_new_obj(mp_obj_str_it_t);
+    o->base.type = &mp_type_str_it;
+    o->str = str;
+    o->cur = 0;
+    return o;
+}
+
+#endif // MICROPY_PY_BUILTINS_STR_UNICODE
diff --git a/py/py.mk b/py/py.mk
index 374bb11d61..549c35d320 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -75,6 +75,7 @@ PY_O_BASENAME = \
 	objset.o \
 	objslice.o \
 	objstr.o \
+	objstrunicode.o \
 	objstringio.o \
 	objtuple.o \
 	objtype.o \
diff --git a/py/stream.c b/py/stream.c
index 07a79248ab..a5a96a8682 100644
--- a/py/stream.c
+++ b/py/stream.c
@@ -33,6 +33,7 @@
 #include "qstr.h"
 #include "obj.h"
 #include "objstr.h"
+#include "runtime.h"
 #include "stream.h"
 #if MICROPY_STREAMS_NON_BLOCK
 #include <errno.h>
@@ -67,6 +68,13 @@ STATIC mp_obj_t stream_read(uint n_args, const mp_obj_t *args) {
     if (n_args == 1 || ((sz = mp_obj_get_int(args[1])) == -1)) {
         return stream_readall(args[0]);
     }
+
+    #if MICROPY_PY_BUILTINS_STR_UNICODE
+    if (!o->type->stream_p->is_bytes) {
+        mp_not_implemented("Reading from unicode text streams by character count");
+    }
+    #endif
+
     byte *buf = m_new(byte, sz);
     int error;
     machine_int_t out_sz = o->type->stream_p->read(o, buf, sz, &error);
diff --git a/py/unicode.c b/py/unicode.c
index 88f835131d..a91e08078e 100644
--- a/py/unicode.c
+++ b/py/unicode.c
@@ -65,14 +65,65 @@ STATIC const uint8_t attr[] = {
     AT_LO, AT_LO, AT_LO, AT_PR, AT_PR, AT_PR, AT_PR, 0
 };
 
+// TODO: Rename to str_get_char
 unichar utf8_get_char(const byte *s) {
+#if MICROPY_PY_BUILTINS_STR_UNICODE
+    unichar ord = *s++;
+    if (!UTF8_IS_NONASCII(ord)) return ord;
+    ord &= 0x7F;
+    for (unichar mask = 0x40; ord & mask; mask >>= 1) {
+        ord &= ~mask;
+    }
+    while (UTF8_IS_CONT(*s)) {
+        ord = (ord << 6) | (*s++ & 0x3F);
+    }
+    return ord;
+#else
     return *s;
+#endif
 }
 
+// TODO: Rename to str_next_char
 const byte *utf8_next_char(const byte *s) {
+#if MICROPY_PY_BUILTINS_STR_UNICODE
+    ++s;
+    while (UTF8_IS_CONT(*s)) {
+        ++s;
+    }
+    return s;
+#else
     return s + 1;
+#endif
 }
 
+machine_uint_t utf8_ptr_to_index(const char *s, const char *ptr) {
+    machine_uint_t i = 0;
+    while (ptr > s) {
+        if (!UTF8_IS_CONT(*--ptr)) {
+            i++;
+        }
+    }
+
+    return i;
+}
+
+// TODO: Rename to str_charlen; return machine_uint_t
+uint unichar_charlen(const char *str, uint len)
+{
+#if MICROPY_PY_BUILTINS_STR_UNICODE
+    uint charlen = 0;
+    for (const char *top = str + len; str < top; ++str) {
+        if (!UTF8_IS_CONT(*str)) {
+            ++charlen;
+        }
+    }
+    return charlen;
+#else
+    return len;
+#endif
+}
+
+// Be aware: These unichar_is* functions are actually ASCII-only!
 bool unichar_isspace(unichar c) {
     return c < 128 && (attr[c] & FL_SPACE) != 0;
 }
diff --git a/py/unicode.h b/py/unicode.h
new file mode 100644
index 0000000000..2468b2fecf
--- /dev/null
+++ b/py/unicode.h
@@ -0,0 +1 @@
+machine_uint_t utf8_ptr_to_index(const byte *s, const byte *ptr);
diff --git a/py/vstr.c b/py/vstr.c
index f8b7e4dabc..9ccc95d49b 100644
--- a/py/vstr.c
+++ b/py/vstr.c
@@ -199,12 +199,48 @@ void vstr_add_byte(vstr_t *vstr, byte b) {
 }
 
 void vstr_add_char(vstr_t *vstr, unichar c) {
-    // TODO UNICODE
+#if MICROPY_PY_BUILTINS_STR_UNICODE
+    // TODO: Can this be simplified and deduplicated?
+    // Is it worth just calling vstr_add_len(vstr, 4)?
+    if (c < 0x80) {
+        byte *buf = (byte*)vstr_add_len(vstr, 1);
+        if (buf == NULL) {
+            return;
+        }
+        *buf = (byte)c;
+    } else if (c < 0x800) {
+        byte *buf = (byte*)vstr_add_len(vstr, 2);
+        if (buf == NULL) {
+            return;
+        }
+        buf[0] = (c >> 6) | 0xC0;
+        buf[1] = (c & 0x3F) | 0x80;
+    } else if (c < 0x10000) {
+        byte *buf = (byte*)vstr_add_len(vstr, 3);
+        if (buf == NULL) {
+            return;
+        }
+        buf[0] = (c >> 12) | 0xE0;
+        buf[1] = ((c >> 6) & 0x3F) | 0x80;
+        buf[2] = (c & 0x3F) | 0x80;
+    } else {
+        assert(c < 0x110000);
+        byte *buf = (byte*)vstr_add_len(vstr, 4);
+        if (buf == NULL) {
+            return;
+        }
+        buf[0] = (c >> 18) | 0xF0;
+        buf[1] = ((c >> 12) & 0x3F) | 0x80;
+        buf[2] = ((c >> 6) & 0x3F) | 0x80;
+        buf[3] = (c & 0x3F) | 0x80;
+    }
+#else
     byte *buf = (byte*)vstr_add_len(vstr, 1);
     if (buf == NULL) {
         return;
     }
     buf[0] = c;
+#endif
 }
 
 void vstr_add_str(vstr_t *vstr, const char *str) {
diff --git a/stmhal/mpconfigport.h b/stmhal/mpconfigport.h
index 28cd90bb01..f5110d8f0a 100644
--- a/stmhal/mpconfigport.h
+++ b/stmhal/mpconfigport.h
@@ -44,6 +44,7 @@
 */
 #define MICROPY_ENABLE_LFN          (1)
 #define MICROPY_LFN_CODE_PAGE       (437) /* 1=SFN/ANSI 437=LFN/U.S.(OEM) */
+#define MICROPY_PY_BUILTINS_STR_UNICODE (0)
 #define MICROPY_PY_BUILTINS_FROZENSET (1)
 #define MICROPY_PY_SYS_EXIT         (1)
 #define MICROPY_PY_SYS_STDFILES     (1)
diff --git a/tests/run-tests b/tests/run-tests
index 8f5f7d470d..c6bc4020d4 100755
--- a/tests/run-tests
+++ b/tests/run-tests
@@ -88,10 +88,10 @@ def run_tests(pyb, tests):
             rm_f(filename_expected)
             rm_f(filename_mupy)
         else:
-            with open(filename_expected, "w") as f:
-                f.write(str(output_expected, "ascii"))
-            with open(filename_mupy, "w") as f:
-                f.write(str(output_mupy, "ascii"))
+            with open(filename_expected, "wb") as f:
+                f.write(output_expected)
+            with open(filename_mupy, "wb") as f:
+                f.write(output_mupy)
             print("FAIL ", test_file)
             failed_tests.append(test_name)
 
diff --git a/tests/unicode/data/utf-8_1.txt b/tests/unicode/data/utf-8_1.txt
new file mode 100644
index 0000000000..d84c480d1d
--- /dev/null
+++ b/tests/unicode/data/utf-8_1.txt
@@ -0,0 +1 @@
+Привет
diff --git a/tests/unicode/file1.py b/tests/unicode/file1.py
new file mode 100644
index 0000000000..554e886743
--- /dev/null
+++ b/tests/unicode/file1.py
@@ -0,0 +1,4 @@
+f = open("unicode/data/utf-8_1.txt")
+l = f.readline()
+print(l)
+print(len(l))
diff --git a/tests/unicode/unicode.py b/tests/unicode/unicode.py
new file mode 100644
index 0000000000..c7e523f06a
--- /dev/null
+++ b/tests/unicode/unicode.py
@@ -0,0 +1,18 @@
+# Test a UTF-8 encoded literal
+s = "asdf©qwer"
+for i in range(len(s)):
+    print("s[%d]: %s   %X"%(i, s[i], ord(s[i])))
+
+# Test all three forms of Unicode escape, and
+# all blocks of UTF-8 byte patterns
+s = "a\xA9\xFF\u0123\u0800\uFFEE\U0001F44C"
+for i in range(-len(s), len(s)):
+    print("s[%d]: %s   %X"%(i, s[i], ord(s[i])))
+    print("s[:%d]: %d chars, '%s'"%(i, len(s[:i]), s[:i]))
+    for j in range(i, len(s)):
+        print("s[%d:%d]: %d chars, '%s'"%(i, j, len(s[i:j]), s[i:j]))
+    print("s[%d:]: %d chars, '%s'"%(i, len(s[i:]), s[i:]))
+
+# Test UTF-8 encode and decode
+enc = s.encode()
+print(enc, enc.decode() == s)
diff --git a/tests/unicode/unicode_index.py b/tests/unicode/unicode_index.py
new file mode 100644
index 0000000000..3c31468a41
--- /dev/null
+++ b/tests/unicode/unicode_index.py
@@ -0,0 +1,6 @@
+print("Привет".find("т"))
+print("Привет".find("П"))
+print("Привет".rfind("т"))
+print("Привет".rfind("П"))
+print("Привет".index("т"))
+print("Привет".index("П"))
diff --git a/tests/unicode/unicode_iter.py b/tests/unicode/unicode_iter.py
new file mode 100644
index 0000000000..f08a4aceed
--- /dev/null
+++ b/tests/unicode/unicode_iter.py
@@ -0,0 +1,4 @@
+for c in "Hello":
+    print(c)
+for c in "Привет":
+    print(c)
diff --git a/tests/unicode/unicode_pos.py b/tests/unicode/unicode_pos.py
new file mode 100644
index 0000000000..6a5982920a
--- /dev/null
+++ b/tests/unicode/unicode_pos.py
@@ -0,0 +1,5 @@
+# str methods with explicit start/end pos
+print("Привет".startswith("П"))
+print("Привет".startswith("р", 1))
+print("абвба".find("а", 1))
+print("абвба".find("а", 1, -1))
diff --git a/unix/mpconfigport.h b/unix/mpconfigport.h
index 1559bdb359..763b34ba3e 100644
--- a/unix/mpconfigport.h
+++ b/unix/mpconfigport.h
@@ -41,6 +41,7 @@
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_STREAMS_NON_BLOCK   (1)
 #define MICROPY_OPT_COMPUTED_GOTO   (1)
+#define MICROPY_PY_BUILTINS_STR_UNICODE (0)
 #define MICROPY_PY_BUILTINS_FROZENSET (1)
 #define MICROPY_PY_SYS_EXIT         (1)
 #define MICROPY_PY_SYS_PLATFORM     "linux"