(Latin: Crab), in astronomy, zodiacal constellation lying between Leo and Gemini at about 8 hours 25 minutes right ascension (the coordinate of the celestial sphere analogous to longitude on the Earth) and 20° north declination (angular distance north of the celestial equator). It contains the well-known star cluster called Praesepe or the Beehive.

In astrology, Cancer is the fourth sign of the zodiac, considered as governing the period c. June 22–c. July 22. Its representation as a crab (or lobster or crayfish) is related to the crab in Greek mythology that pinched Heracles while he was fighting the Lernaean hydra. Crushed by Heracles, the crab was rewarded by Heracles' enemy, Hera, by being placed in the heavens.