The constellation of Hydra, from the Latin Hydra, a female water snake, is one of the largest constellations in the sky. It should not be confused with Hydrus, a male water snake, visible in the southern hemisphere. The brightest star in the constellation of Hydra is Alphard, which lies on the neck of the monster. A meteorite swarm is associated with it, the sigma-Hydrids.
In Greek mythology, the Hydra represents the Lernaean Hydra, a water snake with the body of a multi-headed dog which Hercules killed in one of his twelve labours.