Roman emperor and philosopher; born 26 April 121 in Rome, son of Annius Verus and Domitia Lucilla; originally named M. Annius Verus; became emperor 3 July 161, with name M. Aurelius Antoninus Augustus; at first joint ruler with Lucius Verus; upon Verus's death in 169, Marcus Aurelius ruled alone; he died on a military campaign in Viminacium and Sirmium on 17 March 180. Also known as Antoninus, author of Meditations.