Cassiopeia ( ) or Cassiopea may refer to:

Greek mythology

* Cassiopeia (mother of Andromeda), queen of Aethiopia and mother of Andromeda * Cassiopeia (wife of Phoenix), wife of Phoenix, king of Phoenicia * Cassiopeia, wife of Epaphus, king of Egypt, the son of Zeus and Io; mother of Libya

Science

* Cassiopeia (constellation), a northern constellation representing the queen of Ethiopia ** Cassiopeia A, a supernova remnant in that constellation * ''Cassiopea'', the genus of the "upside-down" jellyfish

Arts and entertainment

Film

* Cassiopeia (1996 film), ''Cassiopeia'' (1996 film), a Brazilian CGI film * Cassiopeia (2022 film), ''Cassiopeia'' (2022 film), a South Korean film

Music

* Cassiopeia (TVXQ), the fan club of South Korean boy band TVXQ * "Cassiopeia", a song by Shabütie (now known as Coheed and Cambria) from their 1999 EP ''The Penelope EP'' * "Cassiopeia", a song by Joanna Newsom from her 2004 album ''The Milk-Eyed Mender'' * "Cassiopeia", a song by Dragonland from their 2006 album ''Astronomy (Dragonland album), Astronomy'' * "Cassiopeia", a song by Sunny Lax from his 2006 EP ''P.U.M.A./Cassiopeia'' * "Cassiopeia", a song by Rain from his 2006 album ''Rain's World'' * "Cassiopeia", a song by Sara Bareilles from her 2013 album ''The Blessed Unrest''

Fictional characters

* Cassiopeia "Cassie" Sullivan, in The 5th Wave (series), ''The 5th Wave'' series written by Rick Yancey * Cassiopeia, a magical tortoise in Michael Ende's fantasy book ''Momo (novel), Momo'' * Cassiopeia (Battlestar Galactica), Cassiopeia (''Battlestar Galactica''), from the television series ''Battlestar Galactica'' * Cassiopea (Encantadia), Cassiopea (''Encantadia''), the first Queen of Lireo in the ''Encantadia'' fantasy series of GMA Network * Cassiopeia, the mother of Octavian in ''The Astonishing Life of Octavian Nothing'' * Cassiopeia, the secret identity of Penny from Pokémon Scarlet and Violet, ''Pokémon Scarlet'' and ''Violet''

Other

* Casio Cassiopeia, a series of pocket PCs * Cassiopeia (train), ''Cassiopeia'' (train), an overnight rail service in Japan * USS Cassiopeia (AK-75), USS ''Cassiopeia'' (AK-75), a cargo ship used by the United States Navy in World War II