Clyde Tolson (1900 - 1975) was associate director of the Federal Bureau of Investigation. He was primarily responsible for personnel and disciplinary matters in the bureau, rather than crime-fighting.

Tolson was born in Laredo, Missouri and moved to Washington, D.C in 1926. After failing his first attempt, he joined the FBI in 1927 and by 1930 had been promoted to assistant director (later associate director).

Hoover described Tolson as his alter ego. The men worked closely together during the day, but also took meals together, went to night clubs together, and vacationed together.

Tolson left the FBI two weeks after Hoover's death in 1972. He inherited Hoover's estate and moved into his home. Tolson is buried a few yards away from Hoover in the Congressional Cemetery.

The close relationship between Hoover and Tolson is often cited as evidence that they were both homosexuals, but there is no direct evidence that this was so.