Samuel B. Thomsen (born July 10, 1931, in Saint Paul, Minnesota)[1] is a former career diplomat who was the first United States Ambassador to the Marshall Islands, serving there from 1987 to 1990.

[2] While serving as Consul at Hue, Thomsen served as a political advisor to the commanding general of the U.S. Marines in Vietnam, Lt. Gen. Lewis Walt, from July 1965 to July 1966.

[1] During Thomsen's service in the Marshall Islands, the office of the U.S. Representative was upgraded to Embassy status.

He graduated from the University of California, Los Angeles in 1957 with a BA degree in political science.

He was executive director of the University Religious Conference of Santa Barbara, California, from 1957 to 1960.