The plane carrying nine people crashed amid southwest Alaska's remote mountains and lakes.
Family spokesman Mitch Rose says Stevens was among five people killed in the crash outside Dillingham, about 325 miles southwest of Anchorage.
Stevens began his career in the days before Alaska statehood and did not leave politics until 2008, when he was convicted on corruption charges weeks before Election Day. A federal judge threw out the verdict because of misconduct by federal prosecutors.
Stevens, a moderate Republican, was appointed in December 1968 and became the longest-serving Republican in Senate history.
EADS