Harry Mason Reid (December 2, 1939 – December 28, 2021) served as U.S. Senator from Nevada for 30 years and as Senate Majority Leader from 2007 to 2015. He is credited as the primary political force behind the establishment of the Advanced Aerospace Threat Identification Program (AATIP), the Pentagon's covert UAP investigation unit funded from 2007 to 2012.

Reid's interest in UAP was longstanding and was partly influenced by his friendship with Nevada businessman Robert Bigelow, a prominent private funder of paranormal and UAP research. Working with Senators Daniel Inouye (D-Hawaii) and Ted Stevens (R-Alaska), Reid secured approximately $22 million in "black money" funding for AATIP through the Senate Appropriations Committee's defense spending bill starting in 2007.

AATIP, which operated under the Defense Intelligence Agency, studied reports of encounters by military personnel with anomalous aerial objects and contracted with Bigelow Aerospace Advanced Space Studies (BAASS) to conduct research and maintain a database of UAP cases and related materials. Reid later stated that he believed some recovered materials had been stored at Bigelow Aerospace facilities in Nevada.

Following the 2017 New York Times exposé of AATIP, Reid publicly confirmed the program's existence and stated his belief that the government should take UAP more seriously as a national security concern. He expressed frustration that the program's funding was terminated in 2012 after other Pentagon officials objected to it. Until his death in 2021, Reid continued to advocate for government transparency on UAP.