John XXI, né Petrus Juliani (1215 - May 20, 1277), a Portuguese also called Pedro Hispano, was pope from 1276 until his death.

Note that the previous pope named John was Pope John XIX and there is no Pope John XX (see article for explanation)

He started his studies at the episcopal school of Lisbon cathedral, and later entered Paris university (although some historians claim that he was educated at Montpellier. Wherever he studied, he concentrated on medicine, theology, and Aristotle's dialetic, logic, physics and metaphysics.

From 1245 to 1250 he taught medicine at Siena university, where he wrote the Summulae Logicales, a reference manual on Aristotelian logic in use in European universities for more than 300 years.

After the death of Pope Adrian V, on August 18, 1276, Pedro Hispano was elected Pope at the conclave of cardinals on September 13, and he was crowned a week later. He died on May 20, 1277, after a piece of the ceiling of Viterbo Cathedral, which was being repaired, fell on his head. He was buried there.

Preceded by: Adrian V

Pope (list)

Succeeded by: Nicholas III

it:Papa Giovanni XXI fr:Jean XXI pt:Papa João XXI