Type 31 may refer to:

• Type 31 frigate, a proposed frigate class of the Royal Navy
• Type 31 75 mm mountain gun, a field gun of the Imperial Japanese Army
• a version of the M2 mortar produced in the Republic of China
• Type 31 Grampus I, a variant of the Bristol Grampus, an early British prototype aircraft
• Villiers 31, an early French passenger aircraft
• Tupolev Tu-85, a Soviet prototype aircraft, designated as Type 31 by the US Air Force
• Hispano-Suiza Type 31, an early Spanish aircraft engine
• Peugeot Type 31, an early French motor vehicle
• an early Datsun motor vehicle
• Type 31 Alphabetical Duplicating Punch, an IBM keypunch

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