Solifugae is an order of arachnids known variously as solifuges, sun spiders, camel spiders, and wind scorpions. The order includes more than 1,000 described species in about 147 genera. Despite their common names, they differ from both order Araneae (spiders) and order Scorpiones (scorpions). Most species of solifuges live in dry climates and feed opportunistically on ground-dwelling arthropods and other small animals. The largest species grow to a length of 12–15 cm (5–6 in), including legs. A number of urban legends exaggerate the size and speed of solifuges, and their potential danger to humans, which is negligible.

The order's name is derived from the Latin sol meaning "sun" and fugere meaning "to flee". Put together, it means "those that flee from the sun". These animals have a number of common names, including sun spiders, wind scorpions, wind spiders, red romans, and camel spiders. In Afrikaans, they are known as haarskeerders ("hair cutters"), and baardskeerders ("beard cutters"), in reference to myths that they cut hair to be used as nest bedding.

Solifuges are moderately small to large arachnids (a few millimeters to several centimeters in body length), with the larger species reaching 12–15 cm (5–6 in) in length, including legs. In practice, the respective lengths of the legs of various species differ greatly, so the resulting figures are often misleading. More practical measurements refer primarily to the body length, quoting leg lengths separately, if at all. The body length is up to 7 cm (3 in). Most species are closer to 5 cm (2 in) long, and some small species are under 1 cm (0.4 in) in head-plus-body length when mature.

Like that of spiders, the body plan of the Solifugae has two main tagmata: The prosoma, or cephalothorax, is the anterior tagma, and the 10-segmented abdomen, or opisthosoma, is the posterior tagma. The abdominal tergites and sternites are separated by large areas of intersegmental membranes, giving it a high degree of flexibility and ability to stretch considerably, which allows it to consume a large amount of food. As can be seen, the solifuge prosoma and opisthosoma are not separated by nearly as clear a constriction and connecting tube or "pedicel" as occurs in the Araneae (spiders). The lack of the pedicel reflects another difference between the Solifugae and spiders, namely that solifuges lack both spinnerets and silk, and as a consequence cannot spin webs. Spiders need considerable mobility of their abdomens in their spinning activities, and the Solifugae have no need for such an adaptation.

The prosoma comprises the head, the mouthparts, and the somites that bear the legs and the pedipalps. It is covered by a carapace, also called a prosomal dorsal shield or peltidium, which is composed of three distinct elements called propeltidium, mesopeltidium, and metapeltidium. The propeltidium contains the eyes, the chelicerae that in most species are conspicuously large, the pedipalps, and the first two pairs of legs. The meso- and metapeltidium contain the third and fourth pairs of legs. The chelicerae serve as jaws, and in many species also are used for stridulation. Unlike scorpions, solifuges do not have a third tagma that forms a "tail".

Solifuges have a pair of large central eyes known as median ocelli. These eyes are oriented at the very front of its cephalothorax and are placed closely together. These eyes have a pigment-cup structure and are covered by a domed outer lens made from the animal's exoskeleton. Below the dome is the animal's retina, a multi-tiered structure with a layer of cells called the vitreous body at its top. Underneath is the thin preretinal membrane, acting as a barrier between the vitreous body above and the rhabdomeres beneath. Rhabdomeres are light-sensitive and function as the eye's photoreceptors. Interspersed between the rhabdomeres are pigment cells. The eye's optic nerve begins at its center and is connected to the axons of numerous rhabdomeres.

In addition to the median eyes, solifuges possess a pair of vestigial lateral ocelli. These eyes are found in pits on the animal's cephalic lobes near the chelicerae. The ocelli's lenses are usually atrophied. However, in some species both nerves and pigment cells are present. In species where lateral eyes are functional, they probably aid in detecting motion or changes in brightness.

Like other arachnids outside the orders of scorpions and the Tetrapulmonata, the Solifugae lack book lungs, instead possessing a well-developed tracheal system that inhales and exhales air through a number of spiracles—one pair between the second and third pair of walking legs, two pairs on the abdomen on abdominal segments three and four, and an unpaired spiracle on the fifth abdominal segment. Air sacs are attached to the branching tracheae, with tracheoles penetrating the epithelia of internal organs. Hemocyanin, a respiratory pigment common in the hemolymph of many arachnids and other arthropods, is absent. As embryos they also have opisthosomal protuberances resembling the pulmonary sacs found in some palpigrades. They utilize discontinuous gas exchange almost identical to that of insects, where they go through periods where the spiracles are closed, followed by a phase with open spiracles to allow gas exchange.