Agatho (born 577?, died 10 January 681) was pope from 678 to 681. A Greek born in Sicily of wealthy and devout parents, he gave away his inheritance after their death and retired to a monastery in Palermo. Although the year of his birth is unknown, he was said to have been over 100 years old at the time of his election. He is noteworthy as the pope who ordered St Wilfrid to be restored to his bishopric at York in 679, and as the first to cease payment of the tribute hitherto paid on election to the emperor at Constantinople. It was during his pontificate that the Sixth Ecumenical Council was held at Constantinople, to which he sent his legates and those from a Roman council held in 679.

He was the first pope to take the papal oath as part of his inauguration.

During his reign the Byzantine Empire abandoned monothelitism, and friendly relations with Rome were restored.

Feast day: 10 January.