Hydra may refer to:

• Hydra (mythology), a monster in Greek mythology
• Hydra (constellation), a group of stars
• Hydra (animal), simple invertebrate animal that lives in the water.
• Hydra (moon), a moon around the planet Pluto

This disambiguation page lists articles associated with the title Hydra. If an internal link led you here, you may wish to change the link to point directly to the intended article.