View-Master is the trademark name of a line of special-format stereoscopes and corresponding View-Master "reels", which are thin cardboard disks containing seven Stereoscopic 3-D pairs of small transparent color photographs on film. It was originally manufactured and sold by Sawyer's.

A stereoscope is a device for viewing a stereoscopic pair of separate images, depicting left-eye and right-eye views of the same scene, as a single three-dimensional image.