731 was a common year starting on Monday 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
  • 731 (2025 film), also known as Evil Unbound , a historical drama film involving such warfare

See also

• List of highways numbered 731

Topics referred to by the same term

This disambiguation page lists articles associated with the same number.
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