Formosus, (born c. 816, Rome?—died April 4, 896, Rome), pope from 891 to 896, whose posthumous trial is one of the most bizarre incidents in papal history.

In 864 he was made cardinal bishop of Porto, Italy, by Pope Nicholas I, who sent him to promote the conversion of Bulgaria. He was assigned missions to France by Pope Adrian II (869) and by Pope John VIII (875) but incurred the latter’s mistrust in 876, presumably over a disagreement regarding the coronation of Charles II. Formosus fled Rome and was excommunicated. Pardoned in 878 in exchange for a promise to remain in exile, he returned to Rome in the 880s and was absolved under Pope Marinus I, who restored him to his see of Porto in 883. During the pontificates of the popes Marinus, St. Adrian III, and Stephen V (VI), Formosus’s influence grew, and he was elected Stephen’s successor in October 891. Attempting to liberate Rome from the Spoletan Holy Roman co-emperors Guy II and his son Lambert, Formosus requested King Arnulf of the East Franks to invade Italy. In Rome in 896 Formosus crowned Arnulf emperor, but, while preparing to attack Spoleto, Arnulf was seized with paralysis and was forced to return to Germany. Formosus died shortly thereafter, leaving the discord unresolved.

At a Roman synod (popularly called the “Cadaver Synod”) conducted by Pope Stephen VI (VII), Formosus’s political enemies had his nine-month-old corpse exhumed, propped up on a throne, and subjected to a mock trial—during which a deacon answered for the corpse. He was accused of violating canon law and of perjury, among other charges. Found guilty, his election as pope was declared invalid, his acts were quashed, and his fingers of consecration were cut off. Formosus’s corpse was then cast into a grave but later thrown into the Tiber River. These acts divided Rome politically, provoking an insurrection that resulted in Stephen’s imprisonment and his death by strangulation. During his brief, 20-day tenure, Pope Theodore II reinstated Formosus’s ordinations and solemnly reburied his body in St. Peter’s Basilica. Pope John IX also condemned Stephen’s synod and burned its acts.