Martin Sigvart Grytbak (6 November 1883 – 24 June 1953) was Norwegian-born American engineer. Martin Sigvart Grytbak was born in Nedre Stjørdal in Nord-Trøndelag, Norway. He graduated as a civil engineer in 1903 from the Norwegian University of Science and Technology (Norges Teknisk-Naturvitenskapelige Universitet) in Trondheim. Between 1903 and 1905, he worked on an extension of the Hell–Sunnan Line. He emigrated in 1905 to the United States and worked as a bridge engineer for the Northern Pacific Railway in Saint Paul. Together with Kristoffer Olsen Oustad, and Frederick William Cappelen. he became one of four innovative and influential engineers who were involved in the design of the great bridges of the Twin Cities.