Antoninus Pius (Latin: Titus Aelius Hadrianus Antoninus Augustus Pius; 19 September 86 – 7 March 161), also known as Antoninus, is Roman Emperor from 138 to 161.

He is a member of the Nerva-Antonine dynasty and the Aurelii.

He does not possess the sobriquet "Pius" until after his accession to the throne.

Almost certainly, he earned the name "Pius" because he compelled the Senate to deify his adoptive father Hadrian; the Historia Augusta, however, suggests that he may have earned the name by saving senators sentenced to death by Hadrian in his later years.