Slow motion is a technique in film-making whereby time appears to be slowed down. It was invented by Austrian August Musger. Typically this is achieved when each film frame is captured at a rate much faster than it will be played back. When replayed at normal speed, time appears to be moving slower. The technical term for slow motion is overcranking, referring to the concept of cranking a handcranked camera faster than normal (i.e. faster than 24 frames per second). High-speed photography is a more sophisticated technique that uses specialized equipment to record fast phenomena, usually for scientific applications.

Slow motion is ubiquitous in modern filmmaking. It is used by diverse directors to achieve diverse effects. Some classic subjects of slow motion include:

• Athletic activities of all kinds, to demonstrate skill and style.
• To recapture a key moment in an athletic game, typically shown as a replay.
• Natural phenomena, such as a drop of water hitting a glass.

Slow motion can also be used for artistic effect, to create a romantic or suspenseful aura or to stress a moment in time. Vsevolod Pudovkin, for instance, used slow motion in a suicide scene in The Deserter, in which a man jumping into a river seems sucked down by the slowly splashing waves. Another example is Face/Off, in which John Woo used the same technique in the movements of a flock of flying pigeons. The Matrix made a distinct success in applying the effect into action scenes through the use of multiple cameras, as well as mixing slow-motion with live action in other scenes. Japanese director Akira Kurosawa was a pioneer using this technique in his 1954 movie Seven Samurai. American Sam Peckinpah was another classic lover of the use of slow motion. The technique is especially associated with explosion effect shots and underwater footage. Slow motion was also used extensively in the film Final Fantasy VII: Advent Children.

The opposite of slow motion is fast motion. Cinematographers refer to fast motion as undercranking since it was originally achieved by cranking a handcranked camera slower than normal. It is often used for comic effect, time lapse or occasional stylistic effect.

The concept of slow motion may have existed before the invention of the motion picture: the Japanese theatrical form Noh employs very slow movements.