Artemia is a genus of aquatic crustaceans also known as brine shrimp or sea monkeys. It is the only genus in the family Artemiidae. The first historical record of the existence of Artemia dates back to the first half of the 10th century from Lake Urmia, Iran, with an example called by an Iranian geographer an "aquatic dog" although the first documented unambiguous record is the report and drawings made by Schlösser in 1757 of animals from Lymington, England. Artemia populations are found worldwide, typically in inland saltwater lakes, but occasionally in oceans. Artemia are able to avoid cohabiting with most types of predators, such as fish, by their ability to live in waters of very high salinity (up to 25%).

The ability of the Artemia to produce dormant eggs, known as cysts, has led to extensive use of Artemia in aquaculture. The cysts may be stored indefinitely and hatched on demand to provide a convenient form of live feed for larval fish and crustaceans. Nauplii of the brine shrimp Artemia constitute the most widely used food item, and over 2,000 metric tons (2,200 short tons) of dry Artemia cysts are marketed worldwide annually with most of the cysts being harvested from the Great Salt Lake in Utah. In addition, the resilience of Artemia makes them ideal animals for running biological toxicity assays and it has become a model organism used to test the toxicity of chemicals. Breeds of Artemia are sold as novelty gifts under the marketing name Sea-Monkeys.

The brine shrimp Artemia comprises a group of seven to nine species very likely to have diverged from an ancestral form living in the Mediterranean area about 5.5 million years ago, around the time of the Messinian salinity crisis.

The Laboratory of Aquaculture & Artemia Reference Center at Ghent University possesses the largest known Artemia cyst collection, a cyst bank containing over 1,700 Artemia population samples collected from different locations around the world.

Artemia is a typical primitive arthropod with a segmented body to which is attached broad leaf-like appendages. The body usually consists of 19 segments, the first 11 of which have pairs of appendages, the next two which are often fused together carry the reproductive organs, and the last segments lead to the tail. The total length is usually about 8–10 millimetres (0.31–0.39 in) for the adult male and 10–12 mm (0.39–0.47 in) for the female, but the width of both sexes, including the legs, is about 4 mm (0.16 in).

The body of Artemia is divided into head, thorax, and abdomen. The entire body is covered with a thin, flexible exoskeleton of chitin to which muscles are attached internally and which is shed periodically. In female Artemia, a moult precedes every ovulation.

For brine shrimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronisation of these functions. Autotomy, the voluntary shedding or dropping of parts of the body for defence, is also controlled locally along the nervous system. Artemia have two types of eyes. They have two widely separated compound eyes mounted on flexible stalks. These compound eyes are the main optical sense organ in adult brine shrimps. The median eye, or the naupliar eye, is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplii, which is functional until the adult stage.

Brine shrimp can tolerate any level of salinity between 2.5% and 25% (25–250 g/L), with an optimal range of 60‰–100‰, and occupy the ecological niche that can protect them from predators. Physiologically, optimal levels of salinity are about 30–35‰, but due to predators at these salt levels, brine shrimp seldom occur in natural habitats at salinities of less than 60–80‰. Locomotion is achieved by the rhythmic beating of the appendages acting in pairs. Respiration occurs on the surface of the legs through fibrous, feather-like plates (lamellar epipodites).