Gaius or Caius was a common Roman praenomen. Some individuals with this name are:

• Pope Caius
• Gaius, the jurist (the rest of his name is unknown)
• Gaius Acilius
• Gaius Antonius
• Gaius Antonius Hybrida
• Gaius Asinius Gallus
• Gaius Asinius Pollio
• Gaius Aurelius Cotta
• Gaius Calpurnius Piso
• Gaius Cassius Longinus
• Gaius Claudius Marcellus
• Gaius Duilius
• Gaius Flaminius
• Gaius Flavius Fimbria
• Gaius Gracchus
• Gaius Julius Alpinus Classicianus
• Gaius Julius Antiochus Epiphanes Philopappus , consul and Syrian prince
• Gaius Julius Caesar, most commonly known as simply "Julius Caesar"
• Gaius Julius Caesar Germanicus, most commonly known by his nickname "Caligula"
• Gaius Julius Caesar Strabo Vopiscus
• Gaius Julius Caesar Vipsanianus (or Gaius Vipsanius Agrippa)
• Gaius Julius Callistus
• Gaius Julius Civilis
• Gaius Julius Eurycles
• Gaius Julius Hyginus
• Gaius Julius Marcus
• Gaius Julius Priscus
• Gaius Julius Solinus
• Gaius Julius Vindex , governor of Lusitania
• Gaius Laelius
• Gaius Licinius Stolo
• Gaius Livius Drusus
• Gaius Lucilius
• Gaius Lutatius Catulus
• Gaius Maecenas
• Gaius Marcius Rutilus
• Gaius Matius
• Gaius Memmius
• Gaius Nautius Rutilus
• Gaius Octavius
• Gaius Oppius
• Gaius Papirius Carbo, a consul of 120 BC
• Gaius Papirius Carbo, a tribune of 90 BC
• Gaius Popillius Laenas
• Gaius Rabirius
• Gaius Rubellius Blandus
• Gaius Sallustius Crispus Passienus
• Gaius Servilius Ahala
• Gaius Servilius Glaucia
• Gaius Suetonius Paulinus
• Gaius Valerius Flaccus
• Gaius Valerius Pudens
• Gaius Vipsanius Agrippa (or Gaius Julius Caesar Vipsanianus)
• Gaius Volusenus

Additionally, Gaius Helen Mohiam is a fictional character in the Dune universe.