The House of Colonna is an Italian noble family that was founded in 1099 by Pietro Colonna, son of Count Gregory III of Tusculum. The family was immensely powerful during the Renaissance era, and the family rivalled the House of Orsini for power in Rome until a papal bull in 1511 ended the conflict. In 1571, the heads of both families married nieces of Pope Sixtus V, and the Colonna family supported the Papacy's secular independence until its 1870 annexation by Italy. The house still exists today.