Mary Louise Preis (born October 10, 1941) is an American politician who represented district 34 in the Maryland House of Delegates.
She received her Master of Science degree in 1967 from Georgetown University's Edmund A. Walsh School of Foreign Service.
She was House Vice-Chair of the Joint Committee on Administrative, Executive and Legislative Review from 1995 until 1999.
Finally, she was a member of the Law and Justice Committee for the National Conference of State Legislatures from 1996 until 1999.
Prior to serving in the Maryland General Assembly, Delegate Preis was a practicing attorney.