35 mm film is the film gauge most commonly used for chemical still photography (see 135 film) and motion pictures. The name of the gauge refers to the width of the photographic film, which consists of strips 34.98 ±0.03 mm (1.377 ±0.001 inches) wide. The standard negative pulldown for movies ("single-frame" format) is four perforations per frame along both edges, which results in 16 frames per foot of film. For still photography, the standard frame has eight perforations on each side. To print an 80-minute feature film on 35 mm film stock can cost US$1,500 to $2,500.

A variety of largely proprietary gauges were devised for the numerous camera and projection systems being developed independently in the late 19th century and early 20th century, ranging from 13 mm to 75 mm (0.51–2.95 in), as well as a variety of film feeding systems. This resulted in cameras, projectors and other equipment having to be calibrated to each gauge. The 35 mm width was first used in 1892 by William Dickson and Thomas Edison, using film stock supplied by George Eastman. The 35 mm width with 4 perforations per frame became accepted as the international standard gauge in 1909, and has remained by far the dominant film gauge for image origination and projection despite challenges from smaller and larger gauges, and from novel formats, because its size allowed for a relatively good tradeoff between the cost of the film stock and the quality of the images captured.