For as long as we have looked to the skies, the question of whether life on Earth is the only life to exist has been at the core of the human experience, driving scientific debate and discovery, shaping spiritual belief, and prompting existential thought across borders and generations. And yet, the idea of extraterrestrial intelligence has been largely seen as a joke, banished to the realm of fantasy and conspiracy. Now, for the first time, the full story of our national obsession with UFOs - and the covert, decades-long search by scientists, the United States military, and the CIA for proof of alien life - is told by bestselling author and Pulitzer Prize finalist Garrett M. Graff in a deeply reported and researched history. It begins in 1947, when two headline-making sightings of strange flying objects—the first near Mount Rainier, Washington, involving a pilot named Kenneth Arnold, and the second a ranch on the outskirts of a New Mexico town called Roswell—prompt the US Air Force's newly formed Department of Defense to create a series of secret programs to determine how unidentified phenomena may pose a threat to national security. Over the next half-century, as the atomic age gives way to the space race and the Cold War, the search continues, bringing together an unexpected group of astronomers, military officials, civilian contactees, and true believers who bring us closer, then further, then closer again, to answering one of our most enduring questions: What exactly is out there? Drawing from original archival research, declassified documents, and interviews with senior intelligence and military officials, Graff brings every moment of this extraordinary quest to life, transporting readers from secret military meetings and congressional hearings, where the validity of the search is debated, to the cluttered offices of UFOlogists and hoaxers determined to see the truth revealed, remote observatories where astronomers monitor the stars, and even the halls of the White House, where staffers and presidents alike eagerly await answers. Filled with twists and turns, and populated by an unforgettable cast of characters, UFO is a thrilling story of science, national security, the secrets of space, and the enduring mysteries of the universe.