Clinton Jencks (March 1, 1918 – December 15, 2005) was an American lifelong activist in labor and social justice causes, most famous for union organizing among New Mexico's miners, acting in the 1954 film Salt of the Earth (where he portrayed "Frank Barnes", a character based on himself), and enduring years of government prosecution (and persecution) for allegedly falsifying a Taft-Hartley non-communist affidavit.

He graduated with a bachelor's degree in economics from the University of Colorado at Boulder in 1939, then moved to St. Louis, where he became active in the Interfaith Youth Council and met his future wife, Virginia Derr.

Clinton and Virginia Jencks helped consolidate a Chicano leadership of Mine-Mill Local 890 and encouraged miners' wives to participate in union affairs.

In 1950, the same year that the Congress of Industrial Organizations (CIO) expelled Mine-Mill for alleged communist domination, New Mexican miners went out on strike at the Empire Zinc Company in Hanover, New Mexico.

In October 1952, the Senate Internal Security Subcommittee (SISS) called on Clinton Jencks to testify in its hearings on communism in Mine-Mill, and on April 23, 1953, during the furor over the production of Salt of the Earth, federal agents arrested him on charges of falsifying a noncommunist affidavit he had signed in 1950.

Jencks found himself blacklisted from employment throughout the Southwest, but in the early 1960s, he won a Woodrow Wilson fellowship to study economics at the University of California, Berkeley.