Cygnus is the Latin word for swan, the romanized form of the ancient Greek κύκνος (kyknos) "swan". It may refer to:
- Cycnus, one of a number of characters in Greek Mythology
- Cygnus (constellation), a northern constellation and one of Ptolemy's 48 constellations, named after a character in Greek Mythology
- Cygnus A, the first and brightest radio galaxy, located within the constellation Cygnus
- Cygnus X-1, a binary system located within the constellation Cygnus, containing a black hole
- Cygnus X-1 duology, a pair of epic songs by the Canadian progressive rock band Rush
- Cygnus X-3, a binary system located within the constellation Cygnus, containing a compact object which is a strange star candidate
- Cygnus Hyōga, a character in the manga and anime Saint Seiya
- Cygnus (genus), the genus of most swans
- "Cygnus...Vismund Cygnus", a song from The Mars Volta album Frances the Mute
- U.S.S. Cygnus, Dr. Reinhardt's ship in the 1979 Walt Disney movie The Black Hole
- Cygnus Alpha, a prison planet and episode of the British science fiction show Blake's 7
- Cygnus Black, a character from the Harry Potter novels, a father of Bellatrix Lestrange, Andromeda Tonks and Narcissa Malfoy
- Cygnus Business Media, a U.S.-based business-to-business publishing company
- Cygnus Solutions, a company that provided commercial support for free software and the original developer of Cygwin
- Cygnus (spacecraft), a space vehicle under development by Orbital Sciences Corporation and Thales Alenia Space
- Gestair Cargo, formerly Cygnus Air, Spanish cargo airline