- U.S. Astronomy and Astrophysics
- UFO
- UFO Activity In New York State
- UFO Briefing Document
- UFO-Fotos aus Österreich
- UFOs
- UFOs and The White House
- UFOs, Chemtrails, and Aliens
- Ukryte siły natury
- Ultima Thule
- Ultraviolet Astronomy and the Quest for the Origin of Life
- Ultraviolet Laser Technology and Applications
- Um Mundo Além Das Estrelas
- Um olhar para o universo: 1a edição
- Um passeio pela Via Láctea
- Uma Noite
- Un caprice du Néant - L'univers et ses merveilles
- Un Universo en Expansión
- Un universo gravitacional
- Un viaggio attraverso Divinazione e Astronomia
- Una giornata con Galileo
- Und wenn es die Zeit nicht gäbe?
- Universal and Unified Field Theory
- Universal Life
- Universe: The Solar System and Beyond
- Universet som et Maleri
- Universis
- Universo Espiritual
- Universum für Neugierige
- Universum och surdegslimpa
- Unknowns of Cosmos
- Unraveling Time
- Unseen Cosmos
- Unser Platz im Kosmos
- Unterwegs im Weltraum
- Uplink - Downlink: A History of the Deep Space Network 1957-1997, Mariner, Viking, Voyager, Galileo,...
- Urania
- Uranus: Planets in Our Solar System Children's Astronomy Edition
- Urknall, Weltall und das Leben