# Hydra

Hydra generally refers to:
* Lernaean Hydra, a many-headed serpent in Greek mythology
* Hydra (genus), a genus of simple freshwater animals belonging to the phylum Cnidaria
Hydra or The Hydra may also refer to:

## Astronomy

* Hydra (constellation)
* Hydra (moon), a satellite of Pluto

## Computing

* Hydra (chess), a chess computer
* Hydra (digital repository), an open-source digital repository software product later renamed Samvera
* Hydra (operating system), an early, discontinued, capability-based, object-oriented microkernel
* Hydra (software), a parallelized network login cracker built in various operating systems
* Hydra (specification), a specification for REST APIs
* Hydra 100, a multi-GPU hardware solution
* HYDRA Game Development Kit, a development system by André LaMothe
* Razer Hydra, a game controller
* NEC HYDRAstor, a storage system

## Fictional entities

* Hydra (comics), a fictional organization in the Marvel Universe
** Hydra (Marvel Cinematic Universe), an organisation in the Marvel Cinematic Universe based on the comics counterpart
* Hydra (Dungeons & Dragons), a fictional monster in D&D
* Hydra (Transformers), a character in Transformers
* The Hydra, a fictional organization in The Phantom
* Hydra, a character in UFO Ultramaiden Valkyrie
* The Hydra, a fictional deity created by Henry Kuttner
** Mother Hydra, the co-ruler of the Deep One race in the Cthulhu Mythos
* The Hydra, a fictional fighter jet in Grand Theft Auto: San Andreas and Grand Theft Auto Online
* The Hydra, a fictional machine in Kirby Air Ride
* Hydra, a boss enemy in the video game Prototype 2

## Film and television

* Hydra (film), a 2009 monster movie
* Hydra (Chuck), a fictional database on Chuck
* Hydra, a fictional Dharma Initiative station on Lost

## Music

* Hydra Entertainment, the hip-hop record label
* Hydra (band), an American southern rock band in the 1970s
* Hydra (E.P.), an E.P. by British ambient duo Main (band), 1991
* Hydra (Otep album), 2013
* Hydra, an album by Satariel, 2005
* Hydra (Toto album), or the title song, 1979
* Hydra (Within Temptation album), 2014
* Hydra, an album by Iris, 2008
* "Hydra", a song by Dir En Grey from Macabre, 2000
* "Hydra", a song by Twilight Force from Dawn of the Dragonstar, 2019
* "HYDRA", a song by Myth & Roid, 2018
* "The Hydra", a song by Le Sserafim from Antifragile, 2022

## People

* Hydra (skater), roller derby skater
* Hydra (wrestler), American professional wrestler
* Hydra, an alias of DJ and producer The Thrillseekers

## Places

* Hydra, Algeria, a neighbourhood and a municipality in Algiers
* Hydra (island), an island of Greece

## Ships

* Hydra (ship), a hydrogen ship
* Greek ironclad Hydra, a French-built ironclad warship launched in 1889
* Greek destroyer Hydra, a Dardo-class destroyer launched in 1932
* Greek frigate Hydra, a MEKO 200-type frigate launched in 1992, lead ship of the Hydra class frigate
* HMS Hydra (1797), a 38-gun fifth rate
* HMS Hydra (1838), a wooden steam paddle sloop
** Hydra-class sloop, a class of British steam sloops
* HMS Hydra (1871), a Cyclops-class turret ship
* HMS Hydra (1912), an Acheron-class destroyer
* HMS Hydra J275), an Algerine-class minesweeper launched in 1942
* HMS Hydra (A144), an oceanographic survey vessel launched in 1965
* Hydra-class minelayer, a class of Dutch 1910s minelayers
* HNLMS Hydra (A854), a Duch Navy diving support vessel

## Other uses

* The Hydra, a literary magazine
* Hydra (association), a German self-help and advocacy group for prostitutes
* Hydra (video game), an arcade and Atari Lynx video game
* Hydra game, a concept in mathematical logic
* Hydra Market, a Russian language dark web marketplace that facilitated trafficking of illegal drugs as well as financial services
* Hydra the Revenge, a roller coaster at Dorney Park in Pennsylvania, US
* Hydra 70, an air-to-ground rocket
* Hydra Technologies, an unmanned aerial vehicle firm
* Hydra Trophy, a trophy of the roller derby WFTDA Championships
* Hydra, a wireless station during World War II at Camp X
* Operation Hydra (Yugoslavia)
* Operation Hydra (1943)