What was the name of Caesar’s adopted son who became the first Roman emperor? Caesar’s adopted son was Octavian, who later became the emperor Augustus.
Octavian was born Gaius Octavius in 63 BC and was Julius Caesar’s grandnephew. Caesar’s will, opened after his assassination in 44 BC, made Octavian his principal heir and adopted son. By accepting the inheritance, Octavian took the name Gaius Julius Caesar and built political support by presenting himself as Caesar’s legitimate successor.
Octavian formed the Second Triumvirate with Mark Antony and Lepidus to defeat Caesar’s assassins. After their alliance broke down, Octavian defeated Antony and Cleopatra at the naval Battle of Actium in 31 BC. In 27 BC, the Senate granted him the honorific name Augustus, under which he ruled until AD 14.
Octavian and Augustus are therefore the same person. “Augustus” is the name he used as emperor, while “Octavian” is the familiar name for his earlier career. Mark Antony was Caesar’s ally, and Caligula and Tiberius were later Roman emperors, not Caesar’s adopted son.