C81

C81 or C-81 may refer to :
 * C81 (album) (1981)
 * C-81 (Michigan county highway)
 * C-81 Reliant, a 1933 military aircraft
 * Campbell Airport's FAA LID code
 * Hodgkin's lymphoma's ICD-10 code
 * NGC 6352's Caldwell catalog number
 * Ruy Lopez's Encyclopaedia of Chess Openings code