The conclave to elect Pope Gregory was the longest conclave in the history of the Catholic Church.

Catholic cardinals are gathering at the Vatican for the 2025 conclave to choose Pope Francis' successor. Here's how long it could take.

Catholic cardinals are gathering at the Vatican for the 2025 conclave to choose Pope Francis' successor. Here's how long it could take.

The election of Pope Gregory X in 1271 took two years and nine months. The cardinals had gathered in the city of Viterbo, about 50 miles north of Rome, where Pope Clement IV died in 1268.

The conclave to elect Pope Gregory was the longest conclave in the history of the Catholic Church.

In the 13th century, it took almost three years — 1,006 days to be exact — to choose Pope Clement IV's successor, making it the longest conclave in the Catholic Church’s history.

The agonizingly drawn-out process to elect a successor to Pope Clement IV unfolded in the central Italian town of Viterbo, north of Rome—and it left a permanent mark on Church history.

For nearly 180 years, papal conclaves have chosen a new pope in three to five days. In centuries past, they've taken a lot longer.