Sprites or red sprites are large-scale electric discharges that occur in the mesosphere, high above thunderstorm clouds, or cumulonimbus, giving rise to a varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground.

Sprites appear as luminous red-orange flashes. They often occur in clusters above the troposphere at an altitude range of 50–90 km (31–56 mi). Sporadic visual reports of sprites go back at least to 1886. They were first photographed on July 4, 1989, by scientists from the University of Minnesota and have subsequently been captured in video recordings thousands of times.

Sprites are sometimes inaccurately called upper-atmospheric lightning. However, they are cold plasma phenomena that lack the hot channel temperatures of tropospheric lightning, so they are more akin to fluorescent tube discharges than to lightning discharges. Sprites are associated with various other upper-atmospheric optical phenomena including blue jets and ELVES.

The earliest known report is by Toynbee and Mackenzie in 1886. Nobel laureate C. T. R. Wilson had suggested in 1925, on theoretical grounds, that electrical breakdown could occur in the upper atmosphere, and in 1956 he witnessed what possibly could have been a sprite. They were first documented photographically on July 6, 1989, when scientists from the University of Minnesota, using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite.

Several years after their discovery they were named sprites (air spirits) after their namesake mythological entity based on their elusive nature. Since the 1989 video capture, sprites have been imaged from the ground, from aircraft and from space, and have become the subject of intensive investigations. A featured high speed video that was captured by Thomas Ashcraft, Jacob L Harley, Matthew G McHarg, and Hans Nielsen in 2019 at about 100,000 frames per second is fast enough to provide better detailing of how sprites develop. However, according to NASA's APOD blog, despite being recorded in photographs and videos for the more than 30 years, the "root cause" of sprite lightning remains unknown, "apart from a general association with positive cloud-to-ground lightning." NASA also notes that not all storms exhibit sprite lightning.

In 2016, sprites were observed during Hurricane Matthew's passage through the Caribbean. The role of sprites in the tropical cyclones is presently unknown.

Sprites have been observed over North America, Central America, South America, Europe, Central Africa (Zaire), Australia, the Sea of Japan and Asia and are believed to occur during most large thunderstorm systems.

Rodger (1999) categorized three types of sprites based on their visual appearance.