Otis Air National Guard Base (IATA: FMH, ICAO: KFMH, FAA LID: FMH) is an Air National Guard installation located within Joint Base Cape Cod, a military training facility located on the western portion of Cape Cod in Barnstable County, Massachusetts, United States. It was known as Otis Air Force Base prior to its transfer from the active duty Air Force to the Air National Guard. In the local community, it is more commonly known as Otis Air Base or simply Otis. It was named in honor of pilot and Boston surgeon Lt. Frank "Jesse" Otis.

Today major units include the Coast Guard Air Station Cape Cod, Coast Guard Base Cape Cod and the 102nd Intelligence Wing. Other units include the wing's 101st Air Operations Squadron, the 253d Cyberspace Engineering Installation Group, the 212th Engineering Installation Squadron, the 267th Combat Communications Squadron, the 202nd Weather Flight, the 3rd Battalion, 126th Aviation Regiment, part of the 29th Infantry Division (Army National Guard), and the Coastal Patrol Squadron 18, Cape Cod Composite Squadron 044-Massachusetts Wing (Civil Air Patrol).

Otis Air National Guard Base is named for pilot, flight surgeon, and eminent Boston City Hospital surgeon Lt. Frank "Jesse" Otis. He was a member of the 101st Observation Squadron who was killed on 11 January 1937 when his Douglas O-46A crashed at Hennepin, Illinois while on a cross-country training mission. In 1938, the landing field area at Camp Edwards was named Otis Field in his memory. Ten years later, the base was renamed Otis Air Force Base in his honor. During the Korean War, it was used by the Army to provide basic training. Until 1973, it was the largest Aerospace Defense Command base in the world. During World War II, the field was known as Naval Auxiliary Air Facility Otis and was a subordinate field for Naval Air Station Quonset Point, Rhode Island.

During the Cold War, the base was a key Aerospace Defense Command (ADC) installation. Activities included the 33rd Fighter Wing, the 4604th Support Squadron supporting the Texas Towers (1956–63), the 60th Fighter-Interceptor Squadron, and the 551st Airborne Early Warning and Control Wing aircraft, flying over the Atlantic Ocean from 1954. The 551st flew the EC-121 Warning Star before moving to Hanscom Air Force Base in 1969. The 551st was also the first Air Force wing to fly the EC-121. The 33rd flew various fighter jets in conjunction with the 60th Fighter Interceptor Squadron. The expanding mission led to the runways being lengthened in 1960. The base was also home to the 26th Air Defense Missile Squadron, which operated BOMARC surface-to-air missiles. The regular air force began leaving Otis in the late 1960s as improvements in radar made the 551st more costly when compared to newer technologies. The 551st and the 60th left Otis when the Air Force began to move the continental air defense mission over to the Air National Guard.

Strategic Air Command maintained the 19th Air Refueling Squadron at Otis AFB flying the KC-97 Stratofreighter. After the squadron inactivated, SAC assigned Detachment 1, 416th Bombardment Wing/ 41st Air Refueling Squadron, based at Griffiss AFB, New York with 2 KC-135 Stratotanker and 2 99th Bombardment Wing / 99th Air Refueling Squadron, Westover AFB, Massachusetts KC-135 Stratotankers on 24 Hour Alert Duty.

After active duty units left, the Massachusetts Air National Guard's 102d Fighter Wing (102 FW) became the main unit at the base, flying fighter and air defense missions. During the Cold War period from 1964 until 2004, the 102 FW operated a variety of air defense and tactical fighter aircraft, including the F-86H Sabre, F-84B/F Thunderstreak, F-100D Super Sabre, F-106A/B Delta Dart and F-15A/B Eagle. The Wing's 101st Tactical Fighter Squadron shared missions with the 33rd Tactical Fighter Wing during the Cold War. In 1987, the 102 FW transitioned to the F-15A Eagle, and, later, to the F-15C Eagle.

The base was also utilized as a stopover for a French Air Force Mirage IV on the way to French Polynesia for Operation Tamoure.

Following the 2005 Base Realignment and Closure Commission, the 102 FW was directed to transfer its F-15 aircraft to its sister unit, the 104th Fighter Wing at Barnes Municipal Airport/ANGB. All F-15 aircraft were transferred by January 2008 and the 102 FW was redesignated as the 102d Intelligence Wing (102 IW), a non-flying unit.