U1, U.I or U-1 may refer to: Mathematics U(1), the degree one unitary group Military U-1, the USAF and US Military's designation for the De Havilland Canada DHC-3 Otter light transport aircraft U-1, Soviet designation for Avro 504 trainer. Multiple German U-boats named U-1 Oberursel U.I, an early German aircraft engine HDMS U-1, a Danish submarine SM U-1, an Austro-Hungarian submarine, lead ship of the U-1 class Entertainment U1 Technology, a game and software developing company Ultima I: The First Age of Darkness, a 1981 video game People U1, alias for Yuvan Shankar Raja (born 1979), a Tamil musician and film composer U-1, the main character in the video game Gitaroo Man for the PlayStation 2/PlayStation Portable Railways LNER Class U1, a 1924 British solitary 2-8-0+0-8-2 Beyer-Garratt locomotive SR U1 class, a class of 2-6-0 locomotives developed from the U Class U-Bahn lines U1 (Berlin U-Bahn) U1 (Frankfurt U-Bahn) U1 (Hamburg U-Bahn) U1 (Munich U-Bahn) U1 (Nuremberg U-Bahn) U1 (Vienna U-Bahn) Technology Secure Digital (SD) Cards, class of speed Apple U1 Other U1, unemployment figure released by Bureau of Labor Statistics U1 spliceosomal RNA, a small nuclear RNA component of the spliceosome involved in pre-mRNA splicing. See also UI (disambiguation) 1U (disambiguation) ca:U1