A cel, short for celluloid, is a transparent sheet on which objects are drawn or painted for animation. Generally, the characters are drawn on cels and laid over a static background drawing. This reduces the number of times an image has to be redrawn and enables studios to split up the production process to different specialised teams. Using this taylorised way to animate has made it possile to produce films much more cost-effectively. The invention of the technique is generally attributed to Earl Hurd, who patented the process in 1914.

CEL is also the abbreviation for Centre d'Essais des Landes, a rocket test facility near Biscarosse, France.