Hydra may refer to one of the following articles:
- Hydra, a creature created by Henry Kuttner.
- "Hydra", a short story by Henry Kuttner.
- Mother Hydra, related to Dagon and the Deep Ones, and created by H.P. Lovecraft in The Shadow Over Innsmouth.
- The Lernaean Hydra, a creature from Greek mythology which has been incorporated into the Mythos.