Otis Air National Guard Base 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.

The Joint Base Cape Cod is a state-designated joint base created by the Commonwealth of Massachusetts and the United States War Department in 1935. Governor James Curley signed the state bill to allocate and purchase land for a military facility, and establishing a formal commission to manage this new state military property and personnel. After 22,000 acres of land was secured on Cape Cod, the Massachusetts National Guard began erecting tents and a basic training program in the following year. Formerly the Massachusetts Military Reservation, it was renamed in 2013 to Joint Base Cape Cod by Massachusetts; although having a name similar to many federal military installations, it has no federal recognition.