Given name Ancient world •
Pope Caius (died 296), Bishop of Rome and martyr •
Caius (bishop of Milan), bishop of Milan in the early 3rd-century, saint •
Caius (presbyter), early 3rd century Christian writer •
Caius Largennius (died c. 50), Roman legionary
Modern era •
Caius of Korea (1571–1624), Catholic missionary, one of the
Martyrs of Japan •
Caius Brediceanu (1879–1953), Romanian politician and diplomat •
Caius Gabriel Cibber (1630–1700), Danish sculptor •
Caius Iacob (1912–1992), Romanian mathematician and politician •
Caius Lungu (1989–2025), Romanian footballer •
Caius Novac (1821–?), Romanian footballer •
Caius Welcker (1885–1939), Dutch footballer
Surname •
Jean Ferdinand Caius (1877–1944), French botanist and naturalist who worked in India •
John Caius the Elder (), English poet •
John Caius (1510–1573), English physician and second founder of Gonville and Caius College, Cambridge •
Thomas Caius (died 1572), English academic and administrator, Fellow and Master of University College, Oxford ==Fictional characters==