John G. Agar (January 31, 1921 – April 7, 2002) was an American actor. He starred alongside John Wayne in the films Sands of Iwo Jima and She Wore a Yellow Ribbon, but was later relegated to B movies, such as Tarantula, The Mole People, The Brain from Planet Arous, Flesh and the Spur, and Hand of Death. He also starred with Lucille Ball in the 1951 movie The Magic Carpet.

Agar was born in Chicago, Illinois, the son of Lillian (née Rogers) and John Agar, Sr., a meat packer (see Agar Hams). He was educated at the Harvard School for Boys in Chicago and Lake Forest Academy in Lake Forest, Illinois and graduated from Trinity-Pawling Preparatory School in Pawling, New York, but did not attend college. He and his family moved from Chicago to Los Angeles in 1942, following his father’s death. During World War II he served in the Army Air Corps, and he was a sergeant at the time he left the army in 1946.