SIG Sauer , is, since the 1970s, a combined brand name of several firearms manufacturing companies, with SIG referring to Swiss Industry Group originally founded 1853, while the latter part comes from Sauer & Sohn, founded in 1751 in Germany and still active there. With Switzerland limiting the export of weapons, the partnership started with the SIG Sauer P220 in 1975.

Several sister companies design and manufacture firearms using the trade name SIG Sauer. It is also a registered brand name. The original company, Schweizerische Waggonfabrik (SWF), later Schweizerische Industrie-Gesellschaft (SIG), went through several selloffs, leaving the SIG Sauer brand spread over several companies. The original SIG is now known as SIG Group and no longer has any firearms business.

The German company branch was SIG Sauer GmbH & Co. KG. It was formed in 1976 as a partnership between Schweizerische Industrie Gesellschaft (SIG) of Switzerland and J.P. Sauer & Sohn of Germany before going defunct in 2020.
The Swiss company is SIG Sauer AG. Its predecessor SIG Arms AG was sold to L&O Holding in western Germany and was first renamed SAN Swiss Arms AG, commonly known as Swiss Arms, and in late 2019 was further renamed SIG Sauer AG.
The American company is Sig Sauer, Inc (stylized as SIG SAUER). Originally established as SIGARMS, it was founded in Virginia in 1985 to import and distribute SIG Sauer firearms into the United States. Its headquarters were moved to New Hampshire in 1990. This company was renamed Sig Sauer, Inc. in 2007, and since 2000 is organizationally separate from SIG Sauer GmbH.
L&O Holding is the parent company of the Swiss SIG Sauer AG and the American Sig Sauer Inc