Duarte, Duke of Guimarães (March 1541, in Almeirim – 28 November 1576, in Évora) was a Portuguese infante (prince), son of Duarte of Portugal, 4th Duke of Guimarães and his wife, Isabel of Braganza.

He served as Constable of the Kingdom, the highest military authority in the Portuguese Empire, second only to the monarch.

He was born posthumously and he inherited his father's titles and estates: the Dukedom of Guimarães.

As member of the State Council he voted, in 1569, for the marriage of King Sebastian to Margaret of Valois (who later became Henry IV's first wife) and, in 1574, he escorted King Sebastian in his first trip to Tangiers, in north Africa.

King Sebastian was jealous of this and several times showed disrespect for Duarte's rank.