grandson of the Roman emperor Augustus (reigned 27 BC–AD 14), who would probably, had he survived Augustus, have succeeded to the imperial throne.

Caesar was the eldest son of Augustus' closest associate, Marcus Vipsanius Agrippa, and Julia, the emperor's daughter. Adopted by Augustus in 17 BC, he was granted proconsular powers in 1 BC for a mission to Armenia, which had been invaded by the Parthians. Gaius established a pro-Roman king on the Armenian throne but was seriously wounded (AD 2) while attempting to suppress an uprising in the area. He eventually died of his wounds on his way back to Italy. His death forced Augustus to adopt Tiberius and make him his successor.