Titus Aelius Hadrianus Antoninus Pius (19 September 86 – 7 March 161) was Roman emperor from AD 138 to 161. He was the fourth of the Five Good Emperors from the Nerva–Antonine dynasty.
 
On his accession, Antoninus's name and style be came Imperator Caesar Titus Aelius Hadrianus Antoninus Augustus. One of his first acts as emperor was to persuade the Senate to grant divine honours to Hadrian, which they had at first refused; his efforts to persuade the Senate to grant these honours is the most likely reason given for his title of Pius (dutiful in affection; compare pietas). Two other reasons for this title are that he would support his aged father-in-law with his hand at Senate meetings and that he had saved those men that Hadrian, during his period of ill health, had condemned to death.