U3

U3 or U-3 may refer to:

Transportation

 * U3, an underground rapid transit line in many major German/Austrian cities:
 * U3 (Berlin U-Bahn)
 * U3 (Frankfurt U-Bahn)
 * U3 (Hamburg U-Bahn)
 * U3 (Munich U-Bahn)
 * U3 (Nuremberg U-Bahn)
 * U3 (Stuttgart Stadtbahn)
 * U3 (Vienna U-Bahn)
 * Avies (IATA code: U3), an Estonian airline
 * Cessna U-3, the military model of the Cessna 310 aircraft
 * German submarine U-3, one of several German submarines
 * Boeing Customer Code for Garuda Indonesia

Computer technology

 * U3 (software), a design specification for USB storage, created by U3, LLC
 * U3, a speed class for Secure Digital (SD) cards
 * U.3, an improvement to the U.2 storage interface standard

Video games

 * Ultima III: Exodus, a 1983 video game
 * Uncharted 3: Drake's Deception, a 2011 video game

Other

 * U3, an unemployment figure released by the United States Bureau of Labor Statistics
 * Small nucleolar RNA U3, a type of non-coding RNA