diff --git a/stdlib/csv.pyi b/stdlib/csv.pyi
index f8ab5f000a04..751e85566f88 100644
--- a/stdlib/csv.pyi
+++ b/stdlib/csv.pyi
@@ -54,6 +54,10 @@ if sys.version_info < (3, 13):
 
 _T = TypeVar("_T")
 
+# Note that this is often the wrong class: it is only useful for sub-classing
+# (e.g. csv.excel). Dialect objects returned at runtime, such as the return
+# value of get_dialect(), are usually _csv.Dialect, which is not a subclass
+# of csv.Dialect.
 class Dialect:
     delimiter: str
     quotechar: str | None