Iullus Antonius (43–2 BC), also known as Iulus, was a magnate and poet in ancient Rome. He was the second son of Roman general Mark Antony and Antony's third wife Fulvia. He is best known for being the famous lover of Julia the Elder. He was the full brother of Marcus Antonius Antyllus, half-brother of Claudia (the first wife of Augustus) through his mother's first marriage, half-brother of Antonia Major and Antonia Minor through his father's marriage to Octavia Minor, and half-brother of Alexander Helios, Cleopatra Selene II and Ptolemy Philadelphus through his father's marriage to Cleopatra VII. His stepsiblings were Marcellus, Claudia Marcella Major (later his wife), Caesarion and Claudia Marcella Minor. He was also stepson to Octavia Minor (sister of Augustus) and Cleopatra VII.