Diane Maura Rosenbaum (born November 26, 1949) is an American politician in the US state of Oregon who was the majority leader of the Oregon State Senate. She was a Democratic member of the Oregon House of Representatives, representing District 42 (Southeast Portland) from 1998 to 2009. She served as speaker pro tempore. In the 2008 elections, she ran unopposed for the Oregon State Senate, replacing Kate Brown, who was elected secretary of state. She won reelection to District 21 in 2012 after defeating Republican Cliff Hutchison.
After Governor John Kitzhaber resigned in February 2015, elevating Brown to the governorship, Rosenbaum was named by The Oregonian as a potential secretary of state. In 2023, Rosenbaum temporarily replaced County Chair Jessica Vega Pederson on the Multnomah County Board of Commissioners. Julia Brim-Edwards was elected to fill the position in the May special election.