C31 or C-31 may refer to: Vehicles Fokker C-31A Troopship, a Dutch military transport , a C-class submarine of the Royal Navy Nissan Laurel C31, a Japanese sedan Sauber C31, a Swiss Formula One car Other uses Blackstripe corydoras, a tropical freshwater fish C-31 highway (Spain), in Catalonia C31 road (Namibia) Bill C-31, various legislation of the Parliament of Canada Caldwell 31, an emission/reflection nebula Channel 31 (disambiguation) King's Gambit, Falkbeer Countergambit, a chess opening C31, a London Cycleway