Duncan Antonio Stewart Agell (1833 – 1923), was a Uruguayan president of Scottish Argentine origin.

He was the son of a marriage between Scotsman Duncan Stewart (of Acharn) and Uruguayan Dorotea Agell.

His niece Matilde Pacheco married José Batlle y Ordóñez, who was later to become a long-serving Uruguayan President.

[2] Later, Stewart opposed the grab of power by Juan Lindolfo Cuestas and was not active in politics from that time.

Duncan Stewart died in 1923, having lived through practically all of Uruguay's post-independence history.