Marie of Prussia (23 January 1579 – 21 February 1649) was a Prussian duchess by birth and Margravine of Brandenburg-Bayreuth by marriage.

Born in Königsberg, Marie was the second daughter of Duke Albert Frederick of Prussia (1553–1618) from his marriage to Marie Eleonore of Cleves (1550–1608), daughter of Duke William the Rich of Jülich-Cleves-Berg.

On 29 April 1604, she married Margrave Christian of Brandenburg-Bayreuth (1581–1655) in Plassenburg Castle.

Since her father left no male heirs, a dispute arose between Prussia and Jülich-Cleves-Berg about Mary's compensation.

[2] Mary and her family in Franconia had to flee their homes during the Thirty Years' War, and the manors were lost.