Hydra may refer to the following:
- Hydra (code) - A UNSC code word for biological threats.
- Hydra system - A colony system of the UNSC.
- Hydra System Massacres - A group of conflicts in UNSC history.
- Multiple Launch Rocket System-1 Hydra Gyroc Launcher - A missile launcher introduced in Halo 5: Guardians.
- This is a disambiguation page—a navigational aid which lists other pages that might otherwise share the same or a similar title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.