Cassius may refer to:
People
- Cassius, an ancient Roman family name, see Cassia gens
- Gaius Cassius Longinus (died 42 BC), Roman senator and a leader of Julius Caesar's assassination
- Avidius Cassius (130–175), usurper Roman Emperor
- Cassius, pen-name of Michael Foot, British politician and writer
- Cassius of Clermont (died c. 260)
- Cassius of Narni (died 558), bishop of Narni
- Cassius Marcellus Clay (disambiguation), several people, including:
- Cassius Clay (1942–2016), birth name of American boxer Muhammad Ali
- Cassius Marcellus Clay Sr. (1912–1989), father of the boxer
- Cassius Marcellus Clay (politician) (1810–1903), American abolitionist, nicknamed the "Lion of White Hall"
- Cassius Dio (c. AD 155 or 163/164 – after 229), Roman historian
- Cassius D. Kalb, an American musician
- Cassius Longinus (disambiguation)
- Cassius Stanley (born 1999), American basketball player
- Cassius Turvey (2007–2022), Aboriginal Australian boy killed in Perth
- Cassius Winston (born 1998), American basketball player
Arts, entertainment, and media
- Cassius (band), a French electronic music duo
- "Cassius" (song), a 2008 song by Foals
- "Cassius", a 2017 song by Fleet Foxes on the album Crack-Up
- Cassius Chrome, a House Robot in Robot Wars
- Cassius Bright, a character in the video game The Legend of Heroes: Trails in the Sky
- Cassius Green, a character in the film Sorry to Bother You
- Cassius au Bellona, a character in Pierce Brown's Red Rising series of novels
Other uses
- Cassius (crocodile), the world's largest captive crocodile
- Purple of Cassius, pigment used in stained-glass work
See also
- Chris Hero AKA Kassius Ohno (born 1979), professional wrestler