A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor.

A single-lens reflex camera is a camera that typically uses a mirror and prism system (hence "reflex" from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured.

A twin-lens reflex camera is a type of camera with two objective lenses of the same focal length.

The history of the single-lens reflex camera begins with the use of a reflex mirror in a camera obscura described in 1676, but it took a long time for the design to succeed for photographic cameras.