Pius I (Greek: Πίος) was the bishop of Rome from c. 140 to his death c. 154,[1] according to the Annuario Pontificio.

He is considered a saint by the Catholic Church with a feast day in 11 July, but it is unclear if he died as a martyr.

Its author identifies himself as a former slave, a fact which has led to speculation that both Hermas and Pius were freedmen.

Although he is said to have ordered the publication of the Liber Pontificalis,[3] in fact compilation of that document was not started before the beginning of the 6th century.

[10] The heretics Valentinus, Cerdon, and Marcion visited Rome in Pius' time, and he is believed to have excommunicated both groups.