The Screen Actors Guild ( SAG ) is an American labor union representing over 120,000 film and television principal performers and background performers worldwide. According to SAG's Mission Statement, the Guild seeks to: negotiate and enforce collective bargaining agreements that establish equitable levels of compensation, benefits, and working conditions for its performers; collect compensation for exploitation of recorded performances by its members, and provide protection against unauthorized use of those performances; and preserve and expand work opportunities for its members.

The Guild was founded in 1933 in an effort to eliminate exploitation of actors in Hollywood who were being forced into oppressive multi-year contracts with the major movie studios that did not include restrictions on work hours or minimum rest periods, and often had clauses that automatically renewed at the studios' discretion. These contracts were notorious for allowing the studios to dictate the public and private lives of the performers who signed them, and most did not have provisions to allow the performer to end the deal.

The Screen Actors Guild is associated with the Associated Actors and Artistes of America (AAAA), which is the primary association of performer's unions in the United States. The AAAA is affiliated with the AFL-CIO. SAG claims exclusive jurisdiction over motion picture performances, and shares jurisdiction of radio, television, Internet, and other new media with its sister union AFTRA, with which it shares 44,000 dual members.

In addition to its main offices in Hollywood, SAG also maintains local branches in several major US cities, including: Phoenix, Boston, New York City, Philadelphia, Washington DC, Nashville, Atlanta, Miami, Dallas, Houston, Chicago, Detroit, Denver, Salt Lake City, San Diego, Seattle, Portland, Las Vegas, Honolulu, and San Francisco.

Since 1995, the guild has annually awarded the Screen Actors Guild Awards, which are considered an indicator of success at the Academy Awards.