diff --git a/xarray/core/types.py b/xarray/core/types.py
index 41078d29c0e..5ec76046e8a 100644
--- a/xarray/core/types.py
+++ b/xarray/core/types.py
@@ -182,7 +182,8 @@ def copy(
 Dims = Union[str, Collection[Hashable], "ellipsis", None]
 
 # FYI in some cases we don't allow `None`, which this doesn't take account of.
-T_ChunkDim: TypeAlias = Union[int, Literal["auto"], None, tuple[int, ...]]
+# FYI the `str` is for a size string, e.g. "16MB", supported by dask.
+T_ChunkDim: TypeAlias = Union[str, int, Literal["auto"], None, tuple[int, ...]]
 # We allow the tuple form of this (though arguably we could transition to named dims only)
 T_Chunks: TypeAlias = Union[T_ChunkDim, Mapping[Any, T_ChunkDim]]
 T_NormalizedChunks = tuple[tuple[int, ...], ...]
diff --git a/xarray/tests/test_dask.py b/xarray/tests/test_dask.py
index 517fc0c2d62..3ac638c3c5f 100644
--- a/xarray/tests/test_dask.py
+++ b/xarray/tests/test_dask.py
@@ -337,13 +337,16 @@ def setUp(self):
             self.data, coords={"x": range(4)}, dims=("x", "y"), name="foo"
         )
 
-    def test_chunk(self):
+    def test_chunk(self) -> None:
         for chunks, expected in [
             ({}, ((2, 2), (2, 2, 2))),
             (3, ((3, 1), (3, 3))),
             ({"x": 3, "y": 3}, ((3, 1), (3, 3))),
             ({"x": 3}, ((3, 1), (2, 2, 2))),
             ({"x": (3, 1)}, ((3, 1), (2, 2, 2))),
+            ({"x": "16B"}, ((1, 1, 1, 1), (2, 2, 2))),
+            ("16B", ((1, 1, 1, 1), (1,) * 6)),
+            ("16MB", ((4,), (6,))),
         ]:
             # Test DataArray
             rechunked = self.lazy_array.chunk(chunks)