Titus Aelius Hadrianus Antoninus Pius (/ˌæntəˈnaɪnəs ˈpaɪəs/; Latin: [antoːˈniːnus ˈpius]; 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.
Born into a senatorial family, Antoninus held various offices during the reign of Emperor Hadrian. He married Hadrian's niece Faustina, and Hadrian adopted him as his son and successor shortly before his death. Antoninus acquired the cognomen Pius after his accession to the throne, either because he compelled the Senate to deify his adoptive father, or because he had saved senators sentenced to death by Hadrian in his later years. His reign is notable for the peaceful state of the Empire, with no major revolts or military incursions during this time. A successful military campaign in southern Scotland early in his reign resulted in the construction of the Antonine Wall.