The counts of Tusculum were the most powerful secular noblemen in Latium, near Rome, in present-day Italy between the 10th and 12th centuries. Several popes and an antipope during the 11th century came from their ranks. They created and perfected the political formula of noble-papacy, wherein the pope was arranged to be elected only from the ranks of the Roman nobles. The pornocracy, the period of influence by powerful female courtesans of the family, also influenced papal history.
The counts of Tusculum remained arbiters of Roman politics and religion for more than a century. In addition to the papal influence, they held lay power through consulships and senatorial membership. Traditionally they were pro-Byzantine and anti-German in their political affiliation.
After 1049, the Tusculan Papacy came to an end with the appointment of Pope Leo IX. In fact, the Tusculan papacy was largely responsible for the reaction known as the Gregorian reform. Subsequent events (from 1062 onwards) confirmed a shift in regional politics as the counts came to side with the Holy Roman Emperors against the Rome of the reformers. In 1059 the papal-decree of Pope Nicholas II established new rules for the papal election, therefore putting an end to the noble-papacy formula.
This list is partially incomplete in the tenth century and the chronology and dates of the various countships are often uncertain. They were only counts from about 1013, lords before.
According to tradition, the successors of the Tusculum counts were the Colonna family, founded by Peter (1099–1151), son of Gregory II and called Peter "de Columna" from his fief of Colonna, east of Rome.