C66 or C-66 may refer to: C-66 (Michigan county highway) Berlin Defence (chess), a chess opening Caldwell 66, a globular cluster Caudron C.66, a French biplane , later renamed HMCS Quebec, a Fiji-class cruiser of the Royal Canadian Navy Lockheed C-66 Lodestar, an American transport aircraft Migration for Employment Convention, 1939 of the International Labour Organization Siemens C66, a mobile phone