Marine Aviation and Training Support Group 21 (MATSG-21) is a United States Marine Corps aviation training group that was originally established in 1922 as the 2nd Aviation Group. During World War II the unit was known as Marine Aircraft Group 21 (MAG-21). Squadrons from MAG-21 fought in many of the opening battles of the war to include the Battle of Wake Island, Battle of Midway and as part of the Cactus Air Force during the Battle of Guadalcanal The group was deactivated following the end of the war and was not reactivated until 2000 when the Marine Aviation Detachment at Naval Air Station Pensacola, Florida was renamed MATSG-21. The core of the MATSG personnel is derived from 175 officer instructors and 550 student naval aviators/naval flight officers.