A C-mount is a type of lens mount commonly found on machine vision cameras and other devices like movie cameras and microscope phototubes.

C-mount lenses provide a male thread, which mates with a female thread on the camera. The thread is nominally 1 inch (25.4 mm) in diameter, with 32 threads per inch. The flange focal distance is 17.526 millimetres for a C mount.

CS-mount has a flange focal distance of 12.526 millimetres but is otherwise the same as C-mount, CS-mount lenses are built for the smaller formats, 1/2 inch and down.

C-mount was created by Bell & Howell for their Filmo 70 cine cameras around 1926.