Area 51 is the common name of a highly classified United States Air Force (USAF) facility within the Nevada Test and Training Range in southern Nevada, 83 miles (134 km) north-northwest of Las Vegas.

A remote detachment administered by Edwards Air Force Base, the facility is officially called Homey Airport (ICAO: KXTA, FAA LID: XTA) or Groom Lake (after the salt flat next to its airfield). Details of its operations are not made public, but the USAF says that it is an open training range, and it is commonly thought to support the development and testing of experimental aircraft and weapons. The USAF and CIA acquired the site in 1955, primarily for flight tests of the Lockheed U-2 aircraft.

All research and occurrences in Area 51 are Top Secret/Sensitive Compartmented Information (TS/SCI). The CIA publicly acknowledged the base's existence on 25 June 2013, through a Freedom of Information Act (FOIA) request filed in 2005; it has declassified documents detailing its history and purpose. The intense secrecy surrounding the base has made it the frequent subject of conspiracy theories and a central component of unidentified flying object (UFO) folklore.

The surrounding area is a popular tourist destination, including the small town of Rachel on the "Extraterrestrial Highway".