Caius is a Roman first name, a spelling of Gaius, whose meaning is uncertain; it is traditionally linked to the Latin gaudere, "to rejoice". It was one of the most common names in ancient Rome, borne by Julius Caesar among many others, and the spelling with C is still used at Gonville and Caius College in Cambridge. Caius hovered between number 1060 and 1512 over the past decade and entered the US top 1000 for the first time in 2025 at number 927.