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.
- MLRS-1 Hydra Gyroc Launcher - A rocket launcher introduced in Halo 5: Guardians.
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