Italian family that ruled Rome late in the 10th century. Its founder is generally agreed to be Crescentius, one of the iudices Romani in 902; a nobleman of the same name, possibly his son, was a member of the court of Alberic, Prince of Rome. The family first attained prominence in 963 when Crescentiux de Caballo Marmoreo took a leading part in the synod convened by Emperor otto i to depose Pope john xii. When there was a revolt in Rome (966) against Otto I's nominee, Pope john xiii, Crescentius' son John killed Count Roffredus, the rebel leader, and in return for this support, Crescentius' daughter, Theodoranda, was allowed to marry the pope's nephew, Benedict, Count of the Sabina. It is generally agreed that this Crescentius de Caballo Marmoreo was a kinsman of Crescentius de Theodora, who in 974 led a revolt against Pope benedict vi, imprisoned him in the castel sant' angelo, and set up as antipope the cardinal deacon Franco, who took the name of Boniface VII. The antipope procured the murder of Benedict VI, but was ejected from Rome by the emperor's representative and fled to Constantinople. Pope benedict vii was then elected, and he granted Crescentius de Theodora full pardon. Some time after 977 Crescentius was professed a monk at SS. Boniface and Alexius, Rome; he died there in 984.
In that year Boniface VII returned from exile and seized power in Rome with the help of John and Crescentius II, the sons of Crescentius de Theodora. Boniface VII imprisoned the lawful pope, john xiv, starved him to death, and reigned in his stead. He created John, son of Crescentius de Theodora, patricius romanorum to assist in governing. When Boniface VII died in 985, John the patrician was responsible for choosing his successor, Pope john xv, formerly cardinal priest of San Vitale. The patrician conducted the temporal government of Rome until his death c. 990; his brother, Crescentius II, then took the title of consul Romanorum, and ruled in Rome, keeping the pope a virtual prisoner at the Lateran. Pope John appealed for help to Emperor otto iii (995), but he died before Otto could reach Rome; the emperor then appointed as John's successor his own cousin, Bruno, who became Pope gregory v in 996. At Gregory V's request Otto pardoned Crescentius II; but when the emperor left Rome in the summer of 996 Crescentius rebelled and drove Gregory from the city. He appointed John Philagathos, the Greek-speaking archbishop of Piacenza as antipope (with the title of John XVI), possibly hoping thus to secure Byzantine support. In 998 Otto III again marched on Rome, deposed the antipope, and restored Gregory V. Crescentius II took refuge in the Castel Sant' Angelo, but the fortress was taken by treachery, and the rebel was executed on the battlements and buried in the church of San Pancrazio. In the 11th and 12th centuries the Castel Sant' Angelo became known as the Turris Crescentii.
In 1002 Crescentius II's son, John, was made patricius Romanorum by Pope sylvester ii, and he remained powerful during the pontificates of john xvii (1003) and john xviii (1004–09). He died in the reign of Pope sergi us iv (1009–12), and political power in Rome then passed to the Tusculani family.
A cadet branch of the Crescentii remained in office as counts of the Sabina and supported John, Bishop of Sabina, when he became antipope with the title of Sylvester III in 1045. In 1060 Pope nicholas ii deprived the Crescentii of the countship of the Sabina, and from then they ceased to influence the history of Rome.
Bibliography: f. a. gregorovius, History of the City of Rome in the Middle Ages, tr. g. w. hamilton, 8 v. (v.1–6 2d ed., 7–8 1st ed. London 1900–09), v.3, 4. g. bossi, "I Crescenzi: Contributo alla storia di Roma dall 900 al 1012," Archivio della società romana di storia patria 38 (1915) 389–399; "I Crescenzi di Sabina stefaniani e ottaviani," ibid. 41 (1918) 111–170. w. kÖlmel, Rom und der Kirchenstaat im 10. und 11. Jahrhundert (Berlin 1935). o. gerstenberg, "Studien zur Geschichte des römischen Adels im Ausgange des 10 Jahrhunderts," Historische Vierteljahrschrift 31 (1937) 1–26. c. cecchelli, I Crescenzi, i Savelli, i Cenci (Rome 1942). p. brezzi, Roma e l'Impero medioevale (Bologna 1947).