C13 or C-13 may refer to:
Science and technology IEC 60320 C13, a polarised, three pole plug used in electric power cables Caterpillar C13 Engine, an engine by Caterpillar Inc. Caldwell 13 (NGC 457, the Owl Cluster or ET Cluster), an open star cluster in the constellation Cassiopeia Carbon-13 (13C), a natural stable isotope of carbon Malignant neoplasm of hypopharynx (ICD-10 code), a head and neck cancer Tridecylic acid, a saturated fatty acid
Military and transportation C13 grenade, the Canadian Forces designation for a M67 grenade Autovia C-13, a highway in Catalonia, Spain HMS C13, a 1906 British C-class submarine LNER Class C13, a steam locomotive class
Other uses Sauber C13, a 1994 racing car 13th century C13, in music, a chord with the structure 1 - 3 - 5 - b7 - 9 - 13 French Defence (Encyclopaedia of Chess Openings code) C13 White Lead (Painting) Convention, 1921, an International Labour Organization Convention