This page is about the Latin praenomen. For a list of individuals with this name, see Gaius (disambiguation).

Gaius ( or ) is a Latin praenomen, or personal name, which was one of the most common names throughout Roman history. The feminine form is Gaia. The praenomen was used by both patrician and plebeian families, and gave rise to the patronymic gens Gavia. The name was regularly abbreviated C., based on the original spelling of Caius, which dates from the period before the letters "C" and "G" were differentiated.