diff --git a/mypyc/lib-rt/CPy.h b/mypyc/lib-rt/CPy.h
index 6360d052fa6d..223a0b3e6be9 100644
--- a/mypyc/lib-rt/CPy.h
+++ b/mypyc/lib-rt/CPy.h
@@ -377,6 +377,7 @@ static inline char CPyDict_CheckSize(PyObject *dict, CPyTagged size) {
 
 PyObject *CPyStr_GetItem(PyObject *str, CPyTagged index);
 PyObject *CPyStr_Split(PyObject *str, PyObject *sep, CPyTagged max_split);
+PyObject *CPyStr_Replace(PyObject *str, PyObject *old_substr, PyObject *new_substr, CPyTagged max_replace);
 PyObject *CPyStr_Append(PyObject *o1, PyObject *o2);
 PyObject *CPyStr_GetSlice(PyObject *obj, CPyTagged start, CPyTagged end);
 bool CPyStr_Startswith(PyObject *self, PyObject *subobj);
diff --git a/mypyc/lib-rt/str_ops.c b/mypyc/lib-rt/str_ops.c
index 87e473e27574..16edc21478dd 100644
--- a/mypyc/lib-rt/str_ops.c
+++ b/mypyc/lib-rt/str_ops.c
@@ -53,6 +53,16 @@ PyObject *CPyStr_Split(PyObject *str, PyObject *sep, CPyTagged max_split)
     return PyUnicode_Split(str, sep, temp_max_split);
 }
 
+PyObject *CPyStr_Replace(PyObject *str, PyObject *old_substr, PyObject *new_substr, CPyTagged max_replace)
+{
+    Py_ssize_t temp_max_replace = CPyTagged_AsSsize_t(max_replace);
+    if (temp_max_replace == -1 && PyErr_Occurred()) {
+        PyErr_SetString(PyExc_OverflowError, "Python int too large to convert to C ssize_t");
+            return NULL;
+    }
+    return PyUnicode_Replace(str, old_substr, new_substr, temp_max_replace);
+}
+
 bool CPyStr_Startswith(PyObject *self, PyObject *subobj) {
     Py_ssize_t start = 0;
     Py_ssize_t end = PyUnicode_GET_LENGTH(self);
diff --git a/mypyc/primitives/str_ops.py b/mypyc/primitives/str_ops.py
index 6eb24be33e51..f12cf997e4a5 100644
--- a/mypyc/primitives/str_ops.py
+++ b/mypyc/primitives/str_ops.py
@@ -109,3 +109,20 @@
     return_type=object_rprimitive,
     c_function_name='CPyStr_GetSlice',
     error_kind=ERR_MAGIC)
+
+# str.replace(old, new)
+method_op(
+    name='replace',
+    arg_types=[str_rprimitive, str_rprimitive, str_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="PyUnicode_Replace",
+    error_kind=ERR_MAGIC,
+    extra_int_constants=[(-1, c_int_rprimitive)])
+
+# str.replace(old, new, count)
+method_op(
+    name='replace',
+    arg_types=[str_rprimitive, str_rprimitive, str_rprimitive, int_rprimitive],
+    return_type=str_rprimitive,
+    c_function_name="CPyStr_Replace",
+    error_kind=ERR_MAGIC)
diff --git a/mypyc/test-data/fixtures/ir.py b/mypyc/test-data/fixtures/ir.py
index bb85a41fbe24..b4a379e86c01 100644
--- a/mypyc/test-data/fixtures/ir.py
+++ b/mypyc/test-data/fixtures/ir.py
@@ -75,6 +75,7 @@ def format(self, *args: Any, **kwargs: Any) -> str: ...
     def upper(self) -> str: pass
     def startswith(self, x: str, start: int=..., end: int=...) -> bool: pass
     def endswith(self, x: str, start: int=..., end: int=...) -> bool: pass
+    def replace(self, old: str, new: str, maxcount: Optional[int] = None) -> str: pass
 
 class float:
     def __init__(self, x: object) -> None: pass
diff --git a/mypyc/test-data/irbuild-str.test b/mypyc/test-data/irbuild-str.test
index c573871d15a4..4a5774c67d64 100644
--- a/mypyc/test-data/irbuild-str.test
+++ b/mypyc/test-data/irbuild-str.test
@@ -103,3 +103,39 @@ L3:
     r5 = r0 != 0
     return r5
 
+[case testStrReplace]
+from typing import Optional
+
+def do_replace(s: str, old_substr: str, new_substr: str, max_count: Optional[int] = None) -> str: 
+    if max_count is not None: 
+        return s.replace(old_substr, new_substr, max_count) 
+    else: 
+        return s.replace(old_substr, new_substr) 
+[out]
+def do_replace(s, old_substr, new_substr, max_count): 
+    s, old_substr, new_substr :: str 
+    max_count :: union[int, None] 
+    r0, r1 :: object 
+    r2, r3 :: bit 
+    r4 :: int 
+    r5, r6 :: str 
+L0: 
+    if is_error(max_count) goto L1 else goto L2 
+L1: 
+    r0 = box(None, 1) 
+    max_count = r0 
+L2: 
+    r1 = box(None, 1) 
+    r2 = max_count == r1 
+    r3 = r2 ^ 1 
+    if r3 goto L3 else goto L4 :: bool 
+L3: 
+    r4 = unbox(int, max_count) 
+    r5 = CPyStr_Replace(s, old_substr, new_substr, r4) 
+    return r5 
+L4: 
+    r6 = PyUnicode_Replace(s, old_substr, new_substr, -1) 
+    return r6 
+L5: 
+    unreachable 
+    
\ No newline at end of file
diff --git a/mypyc/test-data/run-strings.test b/mypyc/test-data/run-strings.test
index 5e5fee818a59..7740e77eb8e3 100644
--- a/mypyc/test-data/run-strings.test
+++ b/mypyc/test-data/run-strings.test
@@ -150,3 +150,12 @@ def test_slicing() -> None:
     assert s[1:big_int] == "oobar"
     assert s[big_int:] == ""
     assert s[-big_int:-1] == "fooba"
+
+def test_str_replace() -> None:
+    a = "foofoofoo"
+    assert a.replace("foo", "bar") == "barbarbar"
+    assert a.replace("foo", "bar", -1) == "barbarbar"
+    assert a.replace("foo", "bar", 1) == "barfoofoo"
+    assert a.replace("foo", "bar", 4) == "barbarbar"
+    assert a.replace("aaa", "bar") == "foofoofoo"
+    assert a.replace("ofo", "xyzw") == "foxyzwxyzwo"