731 (disambiguation)

731 was a common year starting on Monday (link will display the full calendar) of the Julian calendar. It may also refer to:


 * 731 (number)
 * 731 (The X-Files), the tenth episode of the third season of the American science fiction television series The X-Files
 * 731 BC, the ninth year of the 730s BC decade
 * 731 series, an AC electric multiple unit train type operated by Hokkaido Railway Company
 * Area code 731, an area code in the U.S. state of Tennessee
 * Battle of Hill 731, a fierce battle fought during World War II in southern Albania
 * Unit 731, a covert biological and chemical warfare research and development unit of the Imperial Japanese Army