Cassius Longinus may refer to:
In descending chronological order:
- Cassius Longinus, end of 2nd century, beginning of 3rd century, historian only known through FGrHist 259.
- Cassius Longinus (philosopher) (213 – 273 AD), a Greek rhetorician and philosopher
- Gaius Cassius Longinus (consul 30) (fl. 30–41 AD), a Roman jurist and great grandson or nephew of Gaius Cassius Longinus, who committed tyrannicide
- Longinus, also called Cassius in some traditions, a name in Christian tradition for the Roman soldier who allegedly pierced the side of Jesus on the cross
- Gaius Cassius Longinus (c. 86 – 42 BC), usually known as Cassius, a Roman senator and one of Julius Caesar's assassins in 44 BC
- Quintus Cassius Longinus, a tribune in 49 BC and supporter of Julius Caesar
- Lucius Cassius Longinus (praetor 66 BC), and part of the Second Catilinarian conspiracy
- Gaius Cassius Longinus (consul 73 BC)
- Gaius Cassius Longinus (consul 96 BC)
- Lucius Cassius Longinus (consul 107 BC)
- Gaius Cassius Longinus (consul 124 BC)
- Lucius Cassius Longinus Ravilla, consul 127 BC
- Gaius Cassius Longinus (consul 171 BC)