U1, U.I or U-1 may refer to:


* U-1, the aircraft designation of the De Havilland Canada DHC-3 Otter light transport aircraft
* German submarine "U-1", the designation for any one of several German U-boats from 1906 to the present day
* Oberursel U.I, an early German aircraft engine


*U1 or U1-Asami, aliases for Yuichi Asami (born 1971), a Japanese musician working for the Konami Corporation
*U-1, the main character in the video game Gitaroo Man for the Playstation 2/Playstation Portable
* U1 Technology, a game and software developing company


* LNER Class U1, a 1924 British solitary 2-8-0+0-8-2 Beyer-Garratt locomotive
* NCC Class U1, a Northern Counties Committee Irish steam locomotiveSome cities in German-speaking countries have underground rail networks known as U-Bahns.
The first line of these railway systems is often shortened to U-1, which may refer to:
* U1 (Berlin U-Bahn), the oldest line on the Berlin U-Bahn
* U-1, a Frankfurt U-Bahn line
* U-1, a Hamburg U-Bahn line
* U-1, a Munich U-Bahn line
* U-1, a Nuremberg U-Bahn line
* U-1, a Vienna U-Bahn line


* U1, unemployment figure released by Bureau of Labor Statistics

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