Born 815, died 896. Pope of the Roman Catholic Church from October 6, 891 to April 4, 896.
Subject of the infamous Cadaver Synod.
He was made bishop of Porto in 864, was a missionary to Bulgaria in 866 and 867, and he helped excommunicate Photius, the patriarch of Constantinople, in 869.
In 876, Pope John VIII, trying to squelch a rival, excommunicated him on charges of treason, deserting the diocese, and coveting the papacy. He admitted his guilt and was allowed back into the church as a lay member.
The next Pope, Marinus I, restored him as bishop of Porto.
Formosus consecrated Stephen V (VI)
(all "Stephen" popes has a dual number because it is uncertain exactly how many of them there were) and was elected his successor. The fact that he already had been a bishop of Porto (church law forbid leaving one diocese for another) never came up during his lifetime
As pope, he promoted Christianity in English and Germanic lands, and generally kept good relations with Constantinople. He made many political enemies, and this would come back to haunt him after he died.