Cancer (♋︎; Ancient Greek: Καρκίνος, romanized: Karkínos, lit. 'crab', Latin for the "Crab") is the fourth astrological sign in the zodiac, originating from the constellation of Cancer. It spans from 90° to 120° celestial longitude. Under the tropical zodiac, the Sun transits this area between approximately June 22 and July 23.

In astrology, Cancer is the cardinal sign of the Water trigon, which is made up of Cancer, Pisces, and Scorpio. It is one of the six negative signs, and its ruling planet is the Moon. Though some depictions of Cancer feature a lobster, crayfish, scarab beetle or a turtle, the sign is most often represented by the crab, based on the Karkinos. Cancer's opposite sign is Capricorn.