Robert Scott Lazar (; born January 26, 1959) is an American who is primarily known for his claims of having been hired in the late 1980s to reverse-engineer purported extraterrestrial technology at a secret site called "S-4", allegedly located several kilometres south of the United States Air Force facility popularly known as Area 51.
Lazar claims he examined an alien craft that ran on an antimatter reactor powered by element 115, which at the time had not yet been synthesized.
He also claims to have read US government briefing documents that described alien involvement in human affairs over the past 10,000 years.
Lazar's claims resulted in bringing added public attention to Area 51 and fueling conspiracy theories surrounding its classified activities.
Lazar's story has since been analyzed and rejected by skeptics and ufologists alike, including researchers at the Massachusetts Institute of Technology, who point out Lazar was never employed at Nellis Air Force Base and does not hold degrees from MIT or Caltech, as he claims.