diff --git a/Lib/test/test_io/test_memoryio.py b/Lib/test/test_io/test_memoryio.py
index 7f2eddd7ae7839..2ee3a1d1562c8b 100644
--- a/Lib/test/test_io/test_memoryio.py
+++ b/Lib/test/test_io/test_memoryio.py
@@ -859,6 +859,12 @@ class CBytesIOTest(PyBytesIOTest):
     ioclass = io.BytesIO
     UnsupportedOperation = io.UnsupportedOperation
 
+    def test_readinto_overlapping_buffer(self):
+        with self.ioclass(b'abcd') as stream:
+            with stream.getbuffer()[1:] as target:
+                self.assertEqual(stream.readinto(target), 3)
+            self.assertEqual(stream.getvalue(), b'aabc')
+
     def test_getstate(self):
         memio = self.ioclass()
         state = memio.__getstate__()
diff --git a/Misc/NEWS.d/next/Library/2026-10-19-20-38-17.gh-issue-159739.a81270.rst b/Misc/NEWS.d/next/Library/2026-10-19-20-38-17.gh-issue-159739.a81270.rst
new file mode 100644
index 00000000000000..413fc0d7f18f68
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-19-20-38-17.gh-issue-159739.a81270.rst
@@ -0,0 +1 @@
+Fix :class:`io.BytesIO` reads into overlapping views of the same buffer.
diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index 9ea197d29f3096..17ae3a82acad2f 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -670,7 +670,7 @@ _io_BytesIO_readinto_impl(bytesio *self, Py_buffer *buffer)
 
     assert(self->pos + len <= PY_SSIZE_T_MAX);
     assert(len >= 0);
-    memcpy(buffer->buf, PyBytes_AS_STRING(self->buf) + self->pos, len);
+    memmove(buffer->buf, PyBytes_AS_STRING(self->buf) + self->pos, len);
     self->pos += len;
 
     return PyLong_FromSsize_t(len);