diff --git a/hpy/debug/src/autogen_debug_ctx_init.h b/hpy/debug/src/autogen_debug_ctx_init.h
index 79768a67e..11f991a14 100644
--- a/hpy/debug/src/autogen_debug_ctx_init.h
+++ b/hpy/debug/src/autogen_debug_ctx_init.h
@@ -131,6 +131,10 @@ HPyListBuilder debug_ctx_ListBuilder_New(HPyContext *dctx, HPy_ssize_t initial_s
 void debug_ctx_ListBuilder_Set(HPyContext *dctx, HPyListBuilder builder, HPy_ssize_t index, DHPy h_item);
 DHPy debug_ctx_ListBuilder_Build(HPyContext *dctx, HPyListBuilder builder);
 void debug_ctx_ListBuilder_Cancel(HPyContext *dctx, HPyListBuilder builder);
+HPyUnicodeBuilder debug_ctx_UnicodeBuilder_New(HPyContext *dctx, HPy_ssize_t size);
+int debug_ctx_UnicodeBuilder_Add(HPyContext *dctx, HPyUnicodeBuilder builder, const char *item);
+DHPy debug_ctx_UnicodeBuilder_Build(HPyContext *dctx, HPyUnicodeBuilder builder);
+void debug_ctx_UnicodeBuilder_Cancel(HPyContext *dctx, HPyUnicodeBuilder builder);
 HPyTupleBuilder debug_ctx_TupleBuilder_New(HPyContext *dctx, HPy_ssize_t initial_size);
 void debug_ctx_TupleBuilder_Set(HPyContext *dctx, HPyTupleBuilder builder, HPy_ssize_t index, DHPy h_item);
 DHPy debug_ctx_TupleBuilder_Build(HPyContext *dctx, HPyTupleBuilder builder);
@@ -339,6 +343,10 @@ static inline void debug_ctx_init_fields(HPyContext *dctx, HPyContext *uctx)
     dctx->ctx_ListBuilder_Set = &debug_ctx_ListBuilder_Set;
     dctx->ctx_ListBuilder_Build = &debug_ctx_ListBuilder_Build;
     dctx->ctx_ListBuilder_Cancel = &debug_ctx_ListBuilder_Cancel;
+    dctx->ctx_UnicodeBuilder_New = &debug_ctx_UnicodeBuilder_New;
+    dctx->ctx_UnicodeBuilder_Add = &debug_ctx_UnicodeBuilder_Add;
+    dctx->ctx_UnicodeBuilder_Build = &debug_ctx_UnicodeBuilder_Build;
+    dctx->ctx_UnicodeBuilder_Cancel = &debug_ctx_UnicodeBuilder_Cancel;
     dctx->ctx_TupleBuilder_New = &debug_ctx_TupleBuilder_New;
     dctx->ctx_TupleBuilder_Set = &debug_ctx_TupleBuilder_Set;
     dctx->ctx_TupleBuilder_Build = &debug_ctx_TupleBuilder_Build;
diff --git a/hpy/debug/src/autogen_debug_wrappers.c b/hpy/debug/src/autogen_debug_wrappers.c
index 55a42d3d7..486e16295 100644
--- a/hpy/debug/src/autogen_debug_wrappers.c
+++ b/hpy/debug/src/autogen_debug_wrappers.c
@@ -592,6 +592,26 @@ void debug_ctx_ListBuilder_Cancel(HPyContext *dctx, HPyListBuilder builder)
     HPyListBuilder_Cancel(get_info(dctx)->uctx, builder);
 }
 
+HPyUnicodeBuilder debug_ctx_UnicodeBuilder_New(HPyContext *dctx, HPy_ssize_t size)
+{
+    return HPyUnicodeBuilder_New(get_info(dctx)->uctx, size);
+}
+
+int debug_ctx_UnicodeBuilder_Add(HPyContext *dctx, HPyUnicodeBuilder builder, const char *item)
+{
+    return HPyUnicodeBuilder_Add(get_info(dctx)->uctx, builder, item);
+}
+
+DHPy debug_ctx_UnicodeBuilder_Build(HPyContext *dctx, HPyUnicodeBuilder builder)
+{
+    return DHPy_wrap(dctx, HPyUnicodeBuilder_Build(get_info(dctx)->uctx, builder));
+}
+
+void debug_ctx_UnicodeBuilder_Cancel(HPyContext *dctx, HPyUnicodeBuilder builder)
+{
+    HPyUnicodeBuilder_Cancel(get_info(dctx)->uctx, builder);
+}
+
 HPyTupleBuilder debug_ctx_TupleBuilder_New(HPyContext *dctx, HPy_ssize_t initial_size)
 {
     return HPyTupleBuilder_New(get_info(dctx)->uctx, initial_size);
diff --git a/hpy/devel/include/common/runtime/ctx_unicodebuilder.h b/hpy/devel/include/common/runtime/ctx_unicodebuilder.h
new file mode 100644
index 000000000..5b7924369
--- /dev/null
+++ b/hpy/devel/include/common/runtime/ctx_unicodebuilder.h
@@ -0,0 +1,15 @@
+#ifndef HPY_COMMON_RUNTIME_UNICODEBUILDER_H
+#define HPY_COMMON_RUNTIME_UNICODEBUILDER_H
+
+#include <Python.h>
+#include "hpy.h"
+#include "common/hpytype.h"
+
+
+_HPy_HIDDEN HPyUnicodeBuilder ctx_UnicodeBuilder_New(HPyContext *ctx, HPy_ssize_t capacity);
+_HPy_HIDDEN int ctx_UnicodeBuilder_Add(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item);
+_HPy_HIDDEN HPy ctx_UnicodeBuilder_Build(HPyContext *ctx, HPyUnicodeBuilder builder);
+_HPy_HIDDEN void ctx_UnicodeBuilder_Cancel(HPyContext *ctx, HPyUnicodeBuilder builder);
+
+
+#endif /* HPY_COMMON_RUNTIME_UNICODEBUILDER_H */
diff --git a/hpy/devel/include/cpython/hpy.h b/hpy/devel/include/cpython/hpy.h
index da30575ca..27e0c6b92 100644
--- a/hpy/devel/include/cpython/hpy.h
+++ b/hpy/devel/include/cpython/hpy.h
@@ -33,6 +33,7 @@ typedef struct { PyObject *_o; } HPy;
 typedef struct { Py_ssize_t _lst; } HPyListBuilder;
 typedef struct { Py_ssize_t _tup; } HPyTupleBuilder;
 typedef struct { void *_o; } HPyTracker;
+typedef struct { void *_o; } HPyUnicodeBuilder;
 typedef Py_ssize_t HPy_ssize_t;
 typedef Py_hash_t HPy_hash_t;
 
@@ -280,6 +281,7 @@ HPy_AsPyObject(HPyContext *ctx, HPy h)
 #include "../common/runtime/ctx_object.h"
 #include "../common/runtime/ctx_type.h"
 #include "../common/runtime/ctx_listbuilder.h"
+#include "../common/runtime/ctx_unicodebuilder.h"
 #include "../common/runtime/ctx_tracker.h"
 #include "../common/runtime/ctx_tuple.h"
 #include "../common/runtime/ctx_tuplebuilder.h"
@@ -433,4 +435,28 @@ HPyTracker_Close(HPyContext *ctx, HPyTracker ht)
     ctx_Tracker_Close(ctx, ht);
 }
 
+HPyAPI_FUNC(HPyUnicodeBuilder)
+HPyUnicodeBuilder_New(HPyContext *ctx, HPy_ssize_t size)
+{
+    return ctx_UnicodeBuilder_New(ctx, size);
+}
+
+HPyAPI_FUNC(int)
+HPyUnicodeBuilder_Add(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item)
+{
+    return ctx_UnicodeBuilder_Add(ctx, builder, item);
+}
+
+HPyAPI_FUNC(HPy)
+HPyUnicodeBuilder_Build(HPyContext *ctx, HPyUnicodeBuilder builder)
+{
+    return ctx_UnicodeBuilder_Build(ctx, builder);
+}
+
+HPyAPI_FUNC(void)
+HPyUnicodeBuilder_Cancel(HPyContext *ctx, HPyUnicodeBuilder builder)
+{
+    ctx_UnicodeBuilder_Cancel(ctx, builder);
+}
+
 #endif /* !HPy_CPYTHON_H */
diff --git a/hpy/devel/include/universal/autogen_ctx.h b/hpy/devel/include/universal/autogen_ctx.h
index 8863cee20..a90643fd7 100644
--- a/hpy/devel/include/universal/autogen_ctx.h
+++ b/hpy/devel/include/universal/autogen_ctx.h
@@ -210,6 +210,10 @@ struct _HPyContext_s {
     void (*ctx_ListBuilder_Set)(HPyContext *ctx, HPyListBuilder builder, HPy_ssize_t index, HPy h_item);
     HPy (*ctx_ListBuilder_Build)(HPyContext *ctx, HPyListBuilder builder);
     void (*ctx_ListBuilder_Cancel)(HPyContext *ctx, HPyListBuilder builder);
+    HPyUnicodeBuilder (*ctx_UnicodeBuilder_New)(HPyContext *ctx, HPy_ssize_t size);
+    int (*ctx_UnicodeBuilder_Add)(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item);
+    HPy (*ctx_UnicodeBuilder_Build)(HPyContext *ctx, HPyUnicodeBuilder builder);
+    void (*ctx_UnicodeBuilder_Cancel)(HPyContext *ctx, HPyUnicodeBuilder builder);
     HPyTupleBuilder (*ctx_TupleBuilder_New)(HPyContext *ctx, HPy_ssize_t initial_size);
     void (*ctx_TupleBuilder_Set)(HPyContext *ctx, HPyTupleBuilder builder, HPy_ssize_t index, HPy h_item);
     HPy (*ctx_TupleBuilder_Build)(HPyContext *ctx, HPyTupleBuilder builder);
diff --git a/hpy/devel/include/universal/autogen_trampolines.h b/hpy/devel/include/universal/autogen_trampolines.h
index 00203a27c..c52b785a5 100644
--- a/hpy/devel/include/universal/autogen_trampolines.h
+++ b/hpy/devel/include/universal/autogen_trampolines.h
@@ -486,6 +486,22 @@ static inline void HPyListBuilder_Cancel(HPyContext *ctx, HPyListBuilder builder
      ctx->ctx_ListBuilder_Cancel ( ctx, builder ); 
 }
 
+static inline HPyUnicodeBuilder HPyUnicodeBuilder_New(HPyContext *ctx, HPy_ssize_t size) {
+     return ctx->ctx_UnicodeBuilder_New ( ctx, size ); 
+}
+
+static inline int HPyUnicodeBuilder_Add(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item) {
+     return ctx->ctx_UnicodeBuilder_Add ( ctx, builder, item ); 
+}
+
+static inline HPy HPyUnicodeBuilder_Build(HPyContext *ctx, HPyUnicodeBuilder builder) {
+     return ctx->ctx_UnicodeBuilder_Build ( ctx, builder ); 
+}
+
+static inline void HPyUnicodeBuilder_Cancel(HPyContext *ctx, HPyUnicodeBuilder builder) {
+     ctx->ctx_UnicodeBuilder_Cancel ( ctx, builder ); 
+}
+
 static inline HPyTupleBuilder HPyTupleBuilder_New(HPyContext *ctx, HPy_ssize_t initial_size) {
      return ctx->ctx_TupleBuilder_New ( ctx, initial_size ); 
 }
diff --git a/hpy/devel/include/universal/hpy.h b/hpy/devel/include/universal/hpy.h
index b401dc240..1ec11ff1e 100644
--- a/hpy/devel/include/universal/hpy.h
+++ b/hpy/devel/include/universal/hpy.h
@@ -36,6 +36,7 @@ typedef struct _HPy_s { HPy_ssize_t _i; } HPy;
 typedef struct { HPy_ssize_t _lst; } HPyListBuilder;
 typedef struct { HPy_ssize_t _tup; } HPyTupleBuilder;
 typedef struct { HPy_ssize_t _i; } HPyTracker;
+typedef struct { HPy_ssize_t _i; } HPyUnicodeBuilder;
 
 typedef struct _HPyContext_s HPyContext;
 
diff --git a/hpy/devel/src/runtime/ctx_unicodebuilder.c b/hpy/devel/src/runtime/ctx_unicodebuilder.c
new file mode 100644
index 000000000..ea96f3ba7
--- /dev/null
+++ b/hpy/devel/src/runtime/ctx_unicodebuilder.c
@@ -0,0 +1,101 @@
+#include <stddef.h>
+#include <string.h>
+#include <Python.h>
+#include "hpy.h"
+
+#ifdef HPY_UNIVERSAL_ABI
+   // for _h2py and _py2h
+#  include "handles.h"
+#endif
+
+static const Py_ssize_t HPYUNICODEBUILDER_INITIAL_CAPACITY = 1024;
+
+typedef struct {
+    Py_ssize_t capacity;  // allocated handles
+    Py_ssize_t length;
+    char *buf;
+} _PyUnicodeBuilder_s;
+
+#ifdef HPY_UNIVERSAL_ABI
+static inline _PyUnicodeBuilder_s *_hb2pb(HPyUnicodeBuilder ht) {
+    return (_PyUnicodeBuilder_s *) (ht)._i;
+}
+static inline HPyUnicodeBuilder _pb2hb(_PyUnicodeBuilder_s *bp) {
+    return (HPyUnicodeBuilder) {(HPy_ssize_t) (bp)};
+}
+#else
+static inline _PyUnicodeBuilder_s *_hb2pb(HPyUnicodeBuilder ht) {
+    return (_PyUnicodeBuilder_s *) (ht)._o;
+}
+static inline HPyUnicodeBuilder _pb2hb(_PyUnicodeBuilder_s *bp) {
+    return (HPyUnicodeBuilder) {(void *) (bp)};
+}
+#endif
+
+_HPy_HIDDEN HPyUnicodeBuilder
+ctx_UnicodeBuilder_New(HPyContext *ctx, HPy_ssize_t capacity)
+{
+    _PyUnicodeBuilder_s *bp;
+    if (capacity == 0) {
+        // TODO: default value or raise a ValueError?
+        capacity = HPYUNICODEBUILDER_INITIAL_CAPACITY;
+    }
+    capacity++; // always reserve space for the trailing 0
+
+    bp = malloc(sizeof(_PyUnicodeBuilder_s));
+    if (bp == NULL) {
+        HPyErr_NoMemory(ctx);
+        return _pb2hb(0);
+    }
+
+    bp->buf = calloc(1, capacity);
+    if (bp == NULL) {
+        free(bp);
+        HPyErr_NoMemory(ctx);
+        return _pb2hb(0);
+    }
+
+    bp->capacity = capacity;
+    bp->length = 0;
+    return _pb2hb(bp);
+}
+
+_HPy_HIDDEN int
+ctx_UnicodeBuilder_Add(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item)
+{
+    _PyUnicodeBuilder_s *bp = _hb2pb(builder);
+    // TODO: Should we trust the user to submit a 0 terminated string?
+    // The alternative would be to use strnlen and have a maximum allowed length for s
+    int len = strlen(item);
+    if(bp->length + len >= bp->capacity) {
+        // TODO: Have a better reallocation strategy
+        int new_size = bp->capacity + len + 1;
+        bp->buf = realloc(bp->buf, new_size);
+        if(bp->buf == NULL) {
+            free(bp);
+            HPyErr_NoMemory(ctx);
+            return -1;
+        }
+    }
+    strncpy((bp->buf + bp->length), item, (bp->capacity - bp->length));
+    bp->length += len;
+    return 0;
+}
+
+_HPy_HIDDEN HPy
+ctx_UnicodeBuilder_Build(HPyContext *ctx, HPyUnicodeBuilder builder)
+{
+    _PyUnicodeBuilder_s *bp = _hb2pb(builder);
+    HPy h_result = HPyUnicode_FromString(ctx, bp->buf);
+    free(bp->buf);
+    free(bp);
+    return h_result;
+}
+
+_HPy_HIDDEN void
+ctx_UnicodeBuilder_Cancel(HPyContext *ctx, HPyUnicodeBuilder builder)
+{
+    _PyUnicodeBuilder_s *bp = _hb2pb(builder);
+    free(bp->buf);
+    free(bp);
+}
diff --git a/hpy/tools/autogen/parse.py b/hpy/tools/autogen/parse.py
index 149ddf82f..365147007 100644
--- a/hpy/tools/autogen/parse.py
+++ b/hpy/tools/autogen/parse.py
@@ -219,6 +219,10 @@ def _visit_hpyslot_slot(self, node):
     'HPyTracker_Add': None,
     'HPyTracker_ForgetAll': None,
     'HPyTracker_Close': None,
+    'HPyUnicodeBuilder_New': None,
+    'HPyUnicodeBuilder_Add': None,
+    'HPyUnicodeBuilder_Build': None,
+    'HPyUnicodeBuilder_Cancel': None,
     '_HPy_Dump': None,
     'HPy_Type': 'PyObject_Type',
     'HPy_TypeCheck': None,
diff --git a/hpy/tools/autogen/public_api.h b/hpy/tools/autogen/public_api.h
index 34c0a1c67..d68bf0994 100644
--- a/hpy/tools/autogen/public_api.h
+++ b/hpy/tools/autogen/public_api.h
@@ -12,6 +12,7 @@ typedef int size_t;
 typedef int HPyFunc_Signature;
 typedef int cpy_PyObject;
 typedef int HPyListBuilder;
+typedef int HPyUnicodeBuilder;
 typedef int HPyTupleBuilder;
 typedef int HPyTracker;
 typedef int HPy_RichCmpOp;
@@ -282,6 +283,11 @@ void HPyListBuilder_Set(HPyContext *ctx, HPyListBuilder builder,
 HPy HPyListBuilder_Build(HPyContext *ctx, HPyListBuilder builder);
 void HPyListBuilder_Cancel(HPyContext *ctx, HPyListBuilder builder);
 
+HPyUnicodeBuilder HPyUnicodeBuilder_New(HPyContext *ctx, HPy_ssize_t size);
+int HPyUnicodeBuilder_Add(HPyContext *ctx, HPyUnicodeBuilder builder, const char *item);
+HPy HPyUnicodeBuilder_Build(HPyContext *ctx, HPyUnicodeBuilder builder);
+void HPyUnicodeBuilder_Cancel(HPyContext *ctx, HPyUnicodeBuilder builder);
+
 HPyTupleBuilder HPyTupleBuilder_New(HPyContext *ctx, HPy_ssize_t initial_size);
 void HPyTupleBuilder_Set(HPyContext *ctx, HPyTupleBuilder builder,
                          HPy_ssize_t index, HPy h_item);
diff --git a/hpy/universal/src/autogen_ctx_def.h b/hpy/universal/src/autogen_ctx_def.h
index 614be60c3..c537790ca 100644
--- a/hpy/universal/src/autogen_ctx_def.h
+++ b/hpy/universal/src/autogen_ctx_def.h
@@ -136,6 +136,10 @@ struct _HPyContext_s g_universal_ctx = {
     .ctx_ListBuilder_Set = &ctx_ListBuilder_Set,
     .ctx_ListBuilder_Build = &ctx_ListBuilder_Build,
     .ctx_ListBuilder_Cancel = &ctx_ListBuilder_Cancel,
+    .ctx_UnicodeBuilder_New = &ctx_UnicodeBuilder_New,
+    .ctx_UnicodeBuilder_Add = &ctx_UnicodeBuilder_Add,
+    .ctx_UnicodeBuilder_Build = &ctx_UnicodeBuilder_Build,
+    .ctx_UnicodeBuilder_Cancel = &ctx_UnicodeBuilder_Cancel,
     .ctx_TupleBuilder_New = &ctx_TupleBuilder_New,
     .ctx_TupleBuilder_Set = &ctx_TupleBuilder_Set,
     .ctx_TupleBuilder_Build = &ctx_TupleBuilder_Build,
diff --git a/hpy/universal/src/ctx.c b/hpy/universal/src/ctx.c
index 7cd371a47..f23d6eb7c 100644
--- a/hpy/universal/src/ctx.c
+++ b/hpy/universal/src/ctx.c
@@ -6,6 +6,7 @@
 #include "common/runtime/ctx_module.h"
 #include "common/runtime/ctx_object.h"
 #include "common/runtime/ctx_listbuilder.h"
+#include "common/runtime/ctx_unicodebuilder.h"
 #include "common/runtime/ctx_tracker.h"
 #include "common/runtime/ctx_tuple.h"
 #include "common/runtime/ctx_tuplebuilder.h"
diff --git a/setup.py b/setup.py
index 991cee993..b3b1fb0b2 100644
--- a/setup.py
+++ b/setup.py
@@ -61,6 +61,7 @@ def get_scm_config():
                    'hpy/devel/src/runtime/ctx_listbuilder.c',
                    'hpy/devel/src/runtime/ctx_tuple.c',
                    'hpy/devel/src/runtime/ctx_tuplebuilder.c',
+                   'hpy/devel/src/runtime/ctx_unicodebuilder.c',
                    'hpy/debug/src/debug_ctx.c',
                    'hpy/debug/src/debug_ctx_cpython.c',
                    'hpy/debug/src/debug_handles.c',
diff --git a/test/test_hpyunicodebuilder.py b/test/test_hpyunicodebuilder.py
new file mode 100644
index 000000000..8bb1f9c4d
--- /dev/null
+++ b/test/test_hpyunicodebuilder.py
@@ -0,0 +1,23 @@
+from .support import HPyTest
+
+class TestString(HPyTest):
+    def test_unicode_builder(self):
+        mod = self.make_module("""
+            HPyDef_METH(f, "f", f_impl, HPyFunc_NOARGS)
+            static HPy f_impl(HPyContext *ctx, HPy h_self)
+            {
+                HPyUnicodeBuilder builder = HPyUnicodeBuilder_New(ctx, 0);
+                if(HPy_IsNull(builder)) {
+                    HPyErr_SetString(ctx, ctx->h_RuntimeError, "Could not create HPyUnicodeBuilder");
+                    return HPy_NULL;
+                }
+                HPyUnicodeBuilder_Add(ctx, builder, "hello ");
+                HPyUnicodeBuilder_Add(ctx, builder, "world");
+                HPyUnicodeBuilder_Add(ctx, builder, "!");
+                HPy h_string = HPyUnicodeBuilder_Build(ctx, builder);
+                return h_string;
+            }
+            @EXPORT(f)
+            @INIT
+        """)
+        assert mod.f() == "hello world!"