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 CnidariaHydra 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 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

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 (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

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)

See also

Greek ship Hydra, a list of Hellenic Navy vessels
HMS Hydra, a list of British Navy vessels
Hydro (disambiguation)
Hydrus, a small constellation in the deep southern sky
Ghidra, reverse engineering software
All pages with titles beginning with Hydra 
All pages with titles containing Hydra