Clarence A. Boonstra (January 5, 1914 – March 20, 2006)[1][2] was the US Ambassador to Costa Rica from 1967 to 1969.

[1] Boonstra graduated with his bachelor's degree from Michigan State University.

After entering the Foreign Service in 1946, he served as deputy chief of mission and chargé d'affaires in Mexico City.

He served as political adviser to U.S. military forces with the Southern Command in Panama and also as director for South American affairs in the State Department.

During the rule of Juan Perón, he served in Argentina and in Cuba as guerrilla fighters under Fidel Castro that battled to overthrow the Batista government.