303 is a year of the Julian calendar. 303 may also refer to: * 303 (number) * Area code 303, a telephone code assigned to central Colorado * Roland TB-303, a bass synthesizer * .303 British, the .303" calibre rifle and machine-gun cartridge * 303 (comics), comic book miniseries by Garth Ennis and Jacen Burrows * Prometheus (Stargate), also called BC-303 or X-303, fictional spacecraft in the Stargate SG-1 television show * 3OH!3, an electropop band from Boulder, Colorado * "303", also used in Australia and New Zealand to refer to the Lee–Enfield rifle * "303", a song by Kula Shaker from the album K * HTTP 303, a status code for "See other" * SOP 303, a National Communications System standard operating procedure to turn off mobile communications * 303 (band), a British girl group