diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index e2705b353858b..94604fd843df1 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -1214,6 +1214,7 @@ Datetimelike
 - Bug in :func:`DataFrame.from_records` when given a :class:`DataFrame` input with timezone-aware datetime64 columns incorrectly dropping the timezone-awareness (:issue:`51162`)
 - Bug in :func:`to_datetime` was raising ``decimal.InvalidOperation`` when parsing date strings with ``errors='coerce'`` (:issue:`51084`)
 - Bug in :func:`to_datetime` with both ``unit`` and ``origin`` specified returning incorrect results (:issue:`42624`)
+- Bug in :meth:`Series.astype` and :meth:`DataFrame.astype` when converting an object-dtype object containing timezone-aware datetimes or strings to ``datetime64[ns]`` incorrectly localizing as UTC instead of raising ``TypeError`` (:issue:`50140`)
 - Bug in :meth:`.DataFrameGroupBy.quantile` and :meth:`.SeriesGroupBy.quantile` with datetime or timedelta dtypes giving incorrect results for groups containing ``NaT`` (:issue:`51373`)
 - Bug in :meth:`.DataFrameGroupBy.quantile` and :meth:`.SeriesGroupBy.quantile` incorrectly raising with :class:`PeriodDtype` or :class:`DatetimeTZDtype` (:issue:`51373`)