C45 or C-45 may refer to:
Beech C-45 Expeditor, an American military transport aircraft C4.5 algorithm, used to generate a decision tree C45 road (Namibia) Caldwell 45, a spiral galaxy Cannabis Act introduced as Bill C-45 to the Parliament of Canada EADS/Northrop Grumman KC-45, a cancelled air refueling aircraft for the US Air Force Kick Sauber C45, a car competing in the 2025 Formula One World Championship Scotch Game, a chess opening Underground Work (Women) Convention, 1935 of the International Labour Organization Ursus C-45, a Polish tractor C45, a variant of Claridge Hi-Tec/Goncz Pistol rifle C45, a 45-minute audio Compact Cassette tape C45 Scaphandre Autonome, vintage scuba equipment