81

81 may refer to:

• 81 (number)
• one of the years 81 BC, AD 81, 1981, 2081
• The international calling code for Japan
• Nickname for the Hells Angels Motorcycle Club. "H" is the eighth letter of the alphabet, and "A" is the first.
• 81 Terpsichore, a main-belt asteroid
• 81 mm mortar, a military indirect fire weapon