Octavia (AD 40?-62?), Roman empress, the daughter of the Roman emperor Claudius I and his third wife Valeria Messalina. In 52 Octavia married her cousin Nero, who later deserted her at the request of his mistress Poppaea Sabina (lived about ad 60). Through the jealousy of Poppaea, whom Nero married in 62, a charge of adultery was brought against Octavia; she was sent to the island of Pandataria (now Ventotene) and there executed. She is the heroine of a contemporary tragedy erroneously attributed to the Roman philosopher Seneca.