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 2008 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)