The EF 1200 mm f/5.6 L USM is a super-telephoto prime lens that was made by Canon Inc. It uses an EF mount, and is compatible with the Canon EOS camera range. It has a focal length of 1200 mm and so on a digital body with a sensor size of 22.5 mm × 15 mm, such as a Canon EOS 40D or 450D, it provides a 35 mm field of view equivalent to that of a 1920 mm lens. With a body with a sensor size of 28.8 mm × 19.2 mm, such as a Canon EOS-1D Mark IV, the field of view is equivalent to that of a 1560 mm lens.

The EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. Mechanically, it is a bayonet-style mount, and all communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers. The mount was first introduced in 1987.