Jacob Dyneley Beam (March 24, 1908 – August 16, 1993) was an American diplomat.

His father was a German professor at Princeton University, and the younger Beam earned a bachelor's degree in 1929 from Princeton before he joined the US Foreign Service.

During World War II, he served as second secretary of the embassy in London.

From 1966 to 1969 he served as Ambassador to Czechoslovakia, where he was present at the Prague Spring.

Beam's support of Senator Edmund Muskie's visit to Moscow in January 1971 caused President Richard Nixon to remark at a meeting with Henry Kissinger and HR Haldeman to give Beam three more months in the role as ambassador to Moscow and then fire him.