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.

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.

[1] In 2023, Rosenbaum temporarily replaced County Chair Jessica Vega Pederson on the Multnomah County Board of Commissioners.