Alan Arnold Diamonstein (August 20, 1931 – October 17, 2019[1]) was an American attorney and Democratic Party politician.

Diamonstein served in the Virginia House of Delegates from 1968 to 2002, representing parts of Newport News.

Diamonstein chose not to run for reelection in 2001, seeking instead the Democratic nomination for lieutenant governor.

He came in second to Richmond mayor Tim Kaine, who would go on to win in the general election.

This article about a member of the Virginia House of Delegates is a stub.