On 20 January 1045, a Roman faction opposed to Benedict IX expelled him from the city and elected John, Bishop of Sabina, as pope under the name Sylvester III.

The election took place amid intense factional rivalry in Rome during the final phase of Tusculan dominance. Sylvester’s claim to the papacy was short-lived. Within weeks Benedict IX returned, regained control of the city, and displaced him.

The episode formed part of a wider succession crisis that would soon involve Gregory VI and ultimately prompt intervention by Henry III, Holy Roman Emperor at the Council of Sutri in 1046.