The United States Coast Guard Auxiliary was established on June 23, 1939 by an act of Congress as the United States Coast Guard Reserve and re-designated as the Auxiliary on February 19, 1941. It is a volunteer uniformed component of the United States Coast Guard (USCG) and works with the rest of the Coast Guard in all of its varied missions with the exception that Auxiliary Members (Auxiliarists) may only support, but not directly participate in, the Coast Guard's military and law enforcement missions. Auxiliarists are not allowed to carry any weapons while serving in any Auxiliary capacity. As of November 18, 2007 there were 30,074 active Auxiliarists.

Auxiliarists are civilians and volunteers. They are not paid for any service they perform, and they take part in activities at their own discretion. Unlike the active duty and reserve components of the USCG, Auxiliarists are not subject to the Uniform Code of Military Justice (UCMJ).

Auxiliarists usually use their own boats, aircraft and radios (and also serve on Coast Guard assets) in carrying out Coast Guard operation missions, or apply specialized skills such as carpentry, cooking, or professional skills such as medical, legal or computer sciences to assist in Coast Guard missions. When using their own boats, aircraft and radios they first offer their property to the Coast Guard, and upon acceptance, become US Government property while they are performing authorized missions for the Coast Guard.