Merrill Monroe Jensen (July 16, 1905 in Elk Horn, Iowa – January 30, 1980 in Madison, Wisconsin)[1] was an American historian, whose research and writing focused on the ratification of the United States Constitution.

Born in Iowa, Jensen took a job as a teacher in a one-room schoolhouse in South Dakota upon graduating from high school.

Except for a short stint as a historian for the Army Air Corps in 1944, his career was spent at his undergraduate and graduate alma maters.

The replacement of the Articles with the Constitution, Jensen argued, created a system of government that minimized the influence of radical democracy rooted in local politics.

His later scholarship focused heavily on primary documents, and he edited a number of substantial document collections, including The Documentary History of the First Federal Elections, 1788-1790 (launched in 1976 and completed in 1989 by his students Robert A. Becker and Gordon denBoer) and The Documentary History of the Ratification of the Constitution and the Bill of Rights, (launched in 1976 and as of 5 June 2018 filling 29 of a projected 31 volumes).