Ghost crabs are semiterrestrial crabs of the subfamily Ocypodinae. They are common shore crabs in tropical and subtropical regions throughout the world, inhabiting deep burrows in the intertidal zone. They are generalist scavengers and predators of small animals. The name "ghost crab" derives from their nocturnality and their generally pale coloration. They are also sometimes called sand crabs, though the name refers to various other crabs that do not belong to the subfamily.

Characteristics of the subfamily include one claw being larger than the other, thick and elongated eyestalks, and a box-like body. The differences in claw sizes, however, are not as marked as in male fiddler crabs. The subfamily includes 22 species in two genera.

Most ghost crabs have pale-colored bodies that blend in well with the sand, though they are capable of gradually changing body coloration to match their environments and the time of day.

Ghost crabs dig deep burrows near the intertidal zone of open sandy beaches. The burrows are usually composed of a long shaft with a chamber at the end, occasionally with a second entrance shaft. They are semi-terrestrial and breathe oxygen from the air through moistened gills. They must periodically wet their gills with seawater,[1][9] usually by taking water from moist sand or by running into the surf and letting the waves wash over them. However, they can only remain under water for a limited amount of time, as they will drown.

Ghost crabs are generalists, scavenging carrion and debris, as well as preying on small animals, including sea turtle eggs and hatchlings, clams, and other crabs. They are predominantly nocturnal. They remain in their burrows during the hottest part of the day, and throughout the coldest part of the winter.

Ghost crabs are swift runners, darting away at the slightest sign of danger. They either head back to their burrows or plunge into the sea to escape intruders. The gaits of ghost crabs alter as their speed increases. Observations on O. ceratophthalma show it can walk indefinitely using all four pairs of walking legs, occasionally alternating which side leads. At higher speeds, the fourth pair of legs is raised off the ground, and at the highest speeds, the crab runs, using only the first and second pairs of walking legs.

Ghost crabs also have the ability to change colors to match their surroundings by adjusting the concentration and dispersal of pigments within their chromatophores. They can even match the specific colors of the grains of sand in their habitats. However, unlike metachrosis (which is a rapid change of colors), ghost crabs are only capable of morphological color change, which occurs over a longer span of time.

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