Bill Diamond is president and chief executive officer of the SETI Institute, the Mountain View, California, nonprofit incorporated in 1984 to study life in the universe and search for signs of extraterrestrial intelligence. A physics graduate who spent most of his career running technology companies, he was appointed to lead the institute in 2015 and has become a frequent public voice for it on UFOs and unidentified anomalous phenomena, arguing that nothing in the public record shows alien technology in Earth's skies.

Diamond holds a bachelor's degree in physics from Holy Cross and an MBA from Georgetown University. According to his institute biography, he spent more than 30 years in laser photonics, optical communications, X-ray imaging and semiconductor processing, at venture-backed startups and large multinationals alike. He was chief executive of WaveSplitter Technologies, of Denselight Semiconductor in Singapore and of Xradia, an X-ray imaging company now part of Zeiss. He also led the U.S. operations of the Swiss firm COMET AG as president of COMET Technologies USA, and his last post before the institute was in executive management at the optical networking company Oclaro. He serves on the board of the Bay Area Science and Innovation Council and formerly sat on the advisory board of Georgetown's McDonough School of Business.

Diamond set out his position on UAP most fully in an April 2024 interview with Space.com. He said there was no credible evidence of alien technology in the sky and called the idea that the government was concealing such material "totally absurd." A civilization able to cross interstellar distances, he argued, would understand Earth long before arriving, would probably send hardware rather than living crews and would not crash-land in deserts. He paired that dismissal with confidence in life elsewhere, citing the Kepler mission's planet discoveries to argue that the statistical probability of humanity being alone is zero.

He repeated that line to Scientific American in February 2026, after President Trump ordered federal agencies to begin releasing files on UFOs and alien life; the magazine's report argued that the political focus risked obscuring the scientific search. In a June 2026 interview clip that circulated on X, Diamond said the government's latest UAP file release contained nothing new and nothing amounting to scientifically valid evidence of technological life beyond Earth, while saying he did not rule out an extraterrestrial origin in principle. Critics have pushed back: a March 2026 essay in The Sentinel Network argued that major radio searches of the interstellar object 3I/ATLAS, including one by the institute's Allen Telescope Array, were tuned for continuous beacons rather than the passive hardware probe Diamond had said visitors would send first.

Diamond has led a prominent scientific organization devoted to the search for extraterrestrial intelligence through years in which UAP disclosure politics pulled that search into public argument. His consistent public line, that life beyond Earth is almost certain but nothing shows alien visitation, has made him a recurring institutional counterpoint to disclosure advocates.