diff --git a/mypyc/lib-rt/CPy.h b/mypyc/lib-rt/CPy.h
index 1881aa97f308..cf096b1e2324 100644
--- a/mypyc/lib-rt/CPy.h
+++ b/mypyc/lib-rt/CPy.h
@@ -767,6 +767,10 @@ CPyTagged CPyBytes_GetItem(PyObject *o, CPyTagged index);
 PyObject *CPyBytes_Concat(PyObject *a, PyObject *b);
 PyObject *CPyBytes_Join(PyObject *sep, PyObject *iter);
 CPyTagged CPyBytes_Ord(PyObject *obj);
+PyObject *CPyBytes_LjustDefaultFill(PyObject *self, CPyTagged width);
+PyObject *CPyBytes_RjustDefaultFill(PyObject *self, CPyTagged width);
+PyObject *CPyBytes_LjustCustomFill(PyObject *self, CPyTagged width, PyObject *fillbyte);
+PyObject *CPyBytes_RjustCustomFill(PyObject *self, CPyTagged width, PyObject *fillbyte);
 
 
 int CPyBytes_Compare(PyObject *left, PyObject *right);
diff --git a/mypyc/lib-rt/bytes_ops.c b/mypyc/lib-rt/bytes_ops.c
index 6ff34b021a9a..7d1dd363203b 100644
--- a/mypyc/lib-rt/bytes_ops.c
+++ b/mypyc/lib-rt/bytes_ops.c
@@ -4,6 +4,7 @@
 
 #include <Python.h>
 #include "CPy.h"
+#include <string.h>
 
 // Returns -1 on error, 0 on inequality, 1 on equality.
 //
@@ -162,3 +163,97 @@ CPyTagged CPyBytes_Ord(PyObject *obj) {
     PyErr_SetString(PyExc_TypeError, "ord() expects a character");
     return CPY_INT_TAG;
 }
+
+
+PyObject *CPyBytes_RjustDefaultFill(PyObject *self, CPyTagged width) {
+    if (!PyBytes_Check(self)) {
+        PyErr_SetString(PyExc_TypeError, "self must be bytes");
+        return NULL;
+    }
+    Py_ssize_t width_size_t = CPyTagged_AsSsize_t(width);
+    Py_ssize_t len = PyBytes_Size(self);
+    if (width_size_t <= len) {
+        Py_INCREF(self);
+        return self;
+    }
+    Py_ssize_t pad = width_size_t - len;
+    PyObject *result = PyBytes_FromStringAndSize(NULL, width_size_t);
+    if (!result) return NULL;
+    char *res_buf = PyBytes_AsString(result);
+    memset(res_buf, ' ', pad);
+    memcpy(res_buf + pad, PyBytes_AsString(self), len);
+    return result;
+}
+
+
+PyObject *CPyBytes_RjustCustomFill(PyObject *self, CPyTagged width, PyObject *fillbyte) {
+    if (!PyBytes_Check(self)) {
+        PyErr_SetString(PyExc_TypeError, "self must be bytes");
+        return NULL;
+    }
+    if (!PyBytes_Check(fillbyte) || PyBytes_Size(fillbyte) != 1) {
+        PyErr_SetString(PyExc_TypeError, "fillbyte must be a single byte");
+        return NULL;
+    }
+    Py_ssize_t width_size_t = CPyTagged_AsSsize_t(width);
+    Py_ssize_t len = PyBytes_Size(self);
+    if (width_size_t <= len) {
+        Py_INCREF(self);
+        return self;
+    }
+    char fill = PyBytes_AsString(fillbyte)[0];
+    Py_ssize_t pad = width_size_t - len;
+    PyObject *result = PyBytes_FromStringAndSize(NULL, width_size_t);
+    if (!result) return NULL;
+    char *res_buf = PyBytes_AsString(result);
+    memset(res_buf, fill, pad);
+    memcpy(res_buf + pad, PyBytes_AsString(self), len);
+    return result;
+}
+
+
+PyObject *CPyBytes_LjustDefaultFill(PyObject *self, CPyTagged width) {
+    if (!PyBytes_Check(self)) {
+        PyErr_SetString(PyExc_TypeError, "self must be bytes");
+        return NULL;
+    }
+    Py_ssize_t width_size_t = CPyTagged_AsSsize_t(width);
+    Py_ssize_t len = PyBytes_Size(self);
+    if (width_size_t <= len) {
+        Py_INCREF(self);
+        return self;
+    }
+    Py_ssize_t pad = width_size_t - len;
+    PyObject *result = PyBytes_FromStringAndSize(NULL, width_size_t);
+    if (!result) return NULL;
+    char *res_buf = PyBytes_AsString(result);
+    memcpy(res_buf, PyBytes_AsString(self), len);
+    memset(res_buf + len, ' ', pad);
+    return result;
+}
+
+
+PyObject *CPyBytes_LjustCustomFill(PyObject *self, CPyTagged width, PyObject *fillbyte) {
+    if (!PyBytes_Check(self)) {
+        PyErr_SetString(PyExc_TypeError, "self must be bytes");
+        return NULL;
+    }
+    if (!PyBytes_Check(fillbyte) || PyBytes_Size(fillbyte) != 1) {
+        PyErr_SetString(PyExc_TypeError, "fillbyte must be a single byte");
+        return NULL;
+    }
+    Py_ssize_t width_size_t = CPyTagged_AsSsize_t(width);
+    Py_ssize_t len = PyBytes_Size(self);
+    if (width_size_t <= len) {
+        Py_INCREF(self);
+        return self;
+    }
+    char fill = PyBytes_AsString(fillbyte)[0];
+    Py_ssize_t pad = width_size_t - len;
+    PyObject *result = PyBytes_FromStringAndSize(NULL, width_size_t);
+    if (!result) return NULL;
+    char *res_buf = PyBytes_AsString(result);
+    memcpy(res_buf, PyBytes_AsString(self), len);
+    memset(res_buf + len, fill, pad);
+    return result;
+}
diff --git a/mypyc/primitives/bytes_ops.py b/mypyc/primitives/bytes_ops.py
index c88e89d1a2ba..b4fe692fb4cd 100644
--- a/mypyc/primitives/bytes_ops.py
+++ b/mypyc/primitives/bytes_ops.py
@@ -126,3 +126,39 @@
     c_function_name="CPyBytes_Ord",
     error_kind=ERR_MAGIC,
 )
+
+# bytes.rjust(width)
+method_op(
+    name="rjust",
+    arg_types=[bytes_rprimitive, int_rprimitive],
+    return_type=bytes_rprimitive,
+    c_function_name="CPyBytes_RjustDefaultFill",
+    error_kind=ERR_MAGIC,
+)
+
+# bytes.rjust(width, fillbyte)
+method_op(
+    name="rjust",
+    arg_types=[bytes_rprimitive, int_rprimitive, bytes_rprimitive],
+    return_type=bytes_rprimitive,
+    c_function_name="CPyBytes_RjustCustomFill",
+    error_kind=ERR_MAGIC,
+)
+
+# bytes.ljust(width)
+method_op(
+    name="ljust",
+    arg_types=[bytes_rprimitive, int_rprimitive],
+    return_type=bytes_rprimitive,
+    c_function_name="CPyBytes_LjustDefaultFill",
+    error_kind=ERR_MAGIC,
+)
+
+# bytes.ljust(width, fillbyte)
+method_op(
+    name="ljust",
+    arg_types=[bytes_rprimitive, int_rprimitive, bytes_rprimitive],
+    return_type=bytes_rprimitive,
+    c_function_name="CPyBytes_LjustCustomFill",
+    error_kind=ERR_MAGIC,
+)
diff --git a/mypyc/test-data/fixtures/ir.py b/mypyc/test-data/fixtures/ir.py
index 661ae50fd5f3..fb0f277fa39a 100644
--- a/mypyc/test-data/fixtures/ir.py
+++ b/mypyc/test-data/fixtures/ir.py
@@ -173,6 +173,8 @@ def __getitem__(self, i: slice) -> bytes: ...
     def join(self, x: Iterable[object]) -> bytes: ...
     def decode(self, x: str=..., y: str=...) -> str: ...
     def __iter__(self) -> Iterator[int]: ...
+    def ljust(self, width: int, fillchar: bytes | bytearray = b" ") -> bytes: ...
+    def rjust(self, width: int, fillchar: bytes | bytearray = b" ") -> bytes: ...
 
 class bytearray:
     @overload
diff --git a/mypyc/test-data/irbuild-bytes.test b/mypyc/test-data/irbuild-bytes.test
index 476c5ac59f48..e5ef0d6cb004 100644
--- a/mypyc/test-data/irbuild-bytes.test
+++ b/mypyc/test-data/irbuild-bytes.test
@@ -185,3 +185,45 @@ L0:
     r10 = CPyBytes_Build(2, var, r9)
     b4 = r10
     return 1
+
+[case testBytesRjustDefault]
+def f(b: bytes) -> bytes:
+    return b.rjust(6)
+[out]
+def f(b):
+    b, r0 :: bytes
+L0:
+    r0 = CPyBytes_RjustDefaultFill(b, 12)
+    return r0
+
+[case testBytesRjustCustom]
+def f(b: bytes) -> bytes:
+    return b.rjust(8, b'0')
+[out]
+def f(b):
+    b, r0, r1 :: bytes
+L0:
+    r0 = b'0'
+    r1 = CPyBytes_RjustCustomFill(b, 16, r0)
+    return r1
+
+[case testBytesLjustDefault]
+def f(b: bytes) -> bytes:
+    return b.ljust(7)
+[out]
+def f(b):
+    b, r0 :: bytes
+L0:
+    r0 = CPyBytes_LjustDefaultFill(b, 14)
+    return r0
+
+[case testBytesLjustCustom]
+def f(b: bytes) -> bytes:
+    return b.ljust(10, b'_')
+[out]
+def f(b):
+    b, r0, r1 :: bytes
+L0:
+    r0 = b'_'
+    r1 = CPyBytes_LjustCustomFill(b, 20, r0)
+    return r1
diff --git a/mypyc/test-data/run-bytes.test b/mypyc/test-data/run-bytes.test
index 5a285320c849..3b81814d056d 100644
--- a/mypyc/test-data/run-bytes.test
+++ b/mypyc/test-data/run-bytes.test
@@ -374,3 +374,43 @@ class subbytearray(bytearray):
 [file userdefinedbytes.py]
 class bytes:
     pass
+
+[case testBytesRjustLjust]
+from testutil import assertRaises
+
+def rjust_bytes(b: bytes, width: int, fill: bytes = b' ') -> bytes:
+    return b.rjust(width, fill)
+
+def ljust_bytes(b: bytes, width: int, fill: bytes = b' ') -> bytes:
+    return b.ljust(width, fill)
+
+def test_rjust_with_default_fill() -> None:
+    assert rjust_bytes(b'abc', 6) == b'   abc', rjust_bytes(b'abc', 6)
+    assert rjust_bytes(b'abc', 3) == b'abc', rjust_bytes(b'abc', 3)
+    assert rjust_bytes(b'abc', 2) == b'abc', rjust_bytes(b'abc', 2)
+    assert rjust_bytes(b'', 4) == b'    ', rjust_bytes(b'', 4)
+
+def test_rjust_with_custom_fill() -> None:
+    assert rjust_bytes(b'abc', 6, b'0') == b'000abc', rjust_bytes(b'abc', 6, b'0')
+    assert rjust_bytes(b'abc', 5, b'_') == b'__abc', rjust_bytes(b'abc', 5, b'_')
+    assert rjust_bytes(b'abc', 3, b'X') == b'abc', rjust_bytes(b'abc', 3, b'X')
+
+def test_ljust_with_default_fill() -> None:
+    assert ljust_bytes(b'abc', 6) == b'abc   ', ljust_bytes(b'abc', 6)
+    assert ljust_bytes(b'abc', 3) == b'abc', ljust_bytes(b'abc', 3)
+    assert ljust_bytes(b'abc', 2) == b'abc', ljust_bytes(b'abc', 2)
+    assert ljust_bytes(b'', 4) == b'    ', ljust_bytes(b'', 4)
+
+def test_ljust_with_custom_fill() -> None:
+    assert ljust_bytes(b'abc', 6, b'0') == b'abc000', ljust_bytes(b'abc', 6, b'0')
+    assert ljust_bytes(b'abc', 5, b'_') == b'abc__', ljust_bytes(b'abc', 5, b'_')
+    assert ljust_bytes(b'abc', 3, b'X') == b'abc', ljust_bytes(b'abc', 3, b'X')
+
+def test_edge_cases() -> None:
+    assert rjust_bytes(b'abc', 0) == b'abc', rjust_bytes(b'abc', 0)
+    assert ljust_bytes(b'abc', 0) == b'abc', ljust_bytes(b'abc', 0)
+    # fillbyte must be length 1
+    with assertRaises(TypeError):
+        rjust_bytes(b'abc', 5, b'')
+    with assertRaises(TypeError):
+        ljust_bytes(b'abc', 5, b'12')