In the United States, a goon squad is a group of criminals or mercenaries commonly associated with either pro-union violence or anti-union violence. In the case of pro-union violence, a goon squad may be formed by union leaders to intimidate or assault non-union workers, strikebreakers, or parties who do not cooperate with the directives of union leadership. In the case of anti-union violence, goon squads are traditionally hired by employers as an attempt at union busting, and resort to many of the same tactics, including intimidation, espionage, and assault.
During the labor unrest of the late 19th century in the United States, businessmen hired Pinkerton agent goon squads to infiltrate unions, and as guards to keep strikers and suspected unionists out of factories. One of the best known such confrontations was the Homestead Strike of 1892, in which Pinkerton agents were called in to enforce the strikebreaking measures of Henry Clay Frick, acting on behalf of Andrew Carnegie, who was abroad; the ensuing conflicts between Pinkerton agents and striking workers led to several deaths on both sides. The Pinkertons were also used as guards in coal, iron, and lumber disputes in Illinois, Michigan, New York and Pennsylvania, as well as the Great Railroad Strike of 1877.
In some cases, corporations have been formed specifically to provide the services of goon squads. The Corporations Auxiliary Company was a corporation created to conduct "the administration of industrial espionage", providing goon squads and labor spies in exchange for payment. In 1921 the Corporations Auxiliary Company was known to masquerade under a dozen different names, and specialized at electing its agents to union office in order to control or destroy unions.
The term "goon" was reputedly coined by F. L. Allen in 1921, perhaps a variant of the US slang "gooney" which had been around since at least 1872, meaning a simpleton or fool, which may have derived from "gony", applied by sailors to the albatross and similar big, clumsy birds (c.1839). In the late 1930s, E. C. Segar’s comic strip Popeye had a character named "Alice the Goon". It was from this character that large stupid people or stupid things came to popularly be called "goons" and the term entered into general use.  "Goon" evolved into slang for a thug (1938), someone hired by racketeers to terrorize political or industrial opponents (1938), or a German stalag guard for American POWs (1945).
- Labor spies
- Union busting
- Union violence
- "Goon Squad" is a song by Elvis Costello and the Attractions
- "Fashion" (David Bowie song) – goon squad is referenced in the lyrics
- A Visit from the Goon Squad by Jennifer Egan
- "The McClellan Committee hearings, 1957". Bureau of National Affairs. 1958.
- Menefee, Shelden C. (March 26, 1938). "The Decline of Dave Beck". The Nation. 146 (13): 354–355.
- "The Growth of Anti-Unionism". Proceedings of the Constitutional Convention of the AFL-CIO. AFL-CIO (16). 1985.
- Richard C. Cabot, Introduction, The Labor Spy--A Survey of Industrial Espionage, by Sidney Howard and Robert Dunn, Under the Auspices of the Cabot Fund for Industrial Research, published in the Brotherhood of Locomotive Firemen and Enginemen's Magazine, Volume 71, Brotherhood of Locomotive Firemen and Enginemen, 1921, page 27
- Sidney Howard, The Labor Spy, A Survey of Industrial Espionage, Chapter 1, The New Republic, reprinted in Mixer and server, Volume 30, Hotel and Restaurant Employee's International Alliance and Bartenders' International League of America, April 15, 1921, page 43
- John Ayton. The Oxford Dictionary of Slang (1998), pg. 309
- John Ayton. The Oxford Dictionary of Slang (1998), pg. 308
- Robert Hendrickson. Word and Phrase Origins, 4th ed., Facts on File, 2008, pg. 358.
- John Ayton. The Oxford Dictionary of Slang (1998), pg. 114
- John Ayton. The Oxford Dictionary of Slang (1998), pg. 264