Glitter is an assortment of flat, small, reflective particles that are precision cut and come in a variety of shapes, sizes, and colors. Glitter particles resemble confetti, sparkles and sequins, but somewhat smaller.

Since prehistoric times, glitter has been made from many different materials including stones such as malachite, and mica, as well as insects and glass. Uses for glitter include clothing, arts, crafts, cosmetics and body paint. Modern glitter is usually manufactured from the combination of aluminum and plastic, which is rarely recycled and can find its way into aquatic habitats, eventually becoming ingested by animals, leading some scientists to call for bans on plastic glitter.

Glittering surfaces have been found to be used since prehistoric times in the arts and in cosmetics. The modern English word "glitter" comes from the Middle English word gliteren, possibly by way of the Old Norse word glitra. However, as early as 30,000 years ago, mica flakes were used to give cave paintings a glittering appearance. Prehistoric humans are believed to have used cosmetics, made of powdered hematite, a sparkling mineral.

The Ancient Egyptians produced "glitter-like substances from crushed beetles" as well as finely ground green malachite crystal. Researchers believe Mayan temples were sometimes painted with red, green, and grey glitter paint made from mica dust, based on infrared scans of the remnants of paint still found on the structures in present-day Guatemala.

People of the Americas 8,000 years ago were using powdered galena, a form of lead, to produce a bright greyish-white glittering paint used for objects of adornment. The collecting and surface mining of galena was prevalent in the Upper Mississippi Valley region by the Cahokia native peoples, for regional trade both raw and crafted into beads or other objects.

The first production of modern plastic glitter is credited to the American machinist Henry F. Ruschmann who invented a machine to cut photo films and paper in the 1930s. Sometimes, the machine "stuttered," generating small pieces of glossy cellulose that employees picked up and used as "snow" to decorate their Christmas trees, and modern glitter was born. With his partner, Harry Goetz, Ruschmann cut mica into washers and glitter from metallized cellulose acetate film. During World War II, glass glitter became unavailable, so Ruschmann found a market for scrap plastics, which were ground into glitter. In 1943, he purchased Meadowbrook Farm in Bernardsville, New Jersey where he founded Meadowbrook Farm Inventions (MFI) in 1948 to produce industrial glitter. MFI became Meadowbrook Inventions, Inc. in 1953. Ruschmann filed a patent for a mechanism for cross-cutting films as well as other glitter-related inventions. Substrates for cutting glitter expanded from metalized cellulose and aluminum foil to metalized and iridescent film, polyester, PVC, and laminations cut into various shapes.

Today over 20,000 varieties of glitter are manufactured in a vast number of different colors, sizes, and materials. One estimate suggests 10 million pounds (4.5 million kilograms) of glitter was either purchased or produced between the years of 1989 and 2009, however the source provides no evidence or reference point. Commercial glitter ranges in size from 0.002 to .25 inches (0.05 to 6.35 mm) a side. First, flat multi-layered sheets are produced combining plastic, coloring, and reflective material such as aluminium, titanium dioxide, iron oxide, and bismuth oxychloride. A common plastic is PET plastic, but mica can be used. These sheets are then cut into tiny particles of many shapes, including squares, triangles, rectangles, and hexagons.

Before fabrics made with modern glitter, sequins were sewn or woven onto fabric to give it a glittering appearance. Edible glitter made from gum arabic and other ingredients is even used by culinary artists.