In this period the renovated Church was again attracting pilgrims and prelates from all the Christian world, and money with them: even with a population of only 30,000, Rome was again becoming a city of consumers dependent upon the presence of a governmental bureaucracy. In the meantime,Italian cities were acquiring increasing autonomy, mainly led by new families which were replacing the old aristocracy and a new class formed by entrepreneurs, traders and merchants. After the sack of Rome by the Normans in 1084, the rebuilding of the city was supported by powerful families such as the Frangipane family and the Pierleoni family, whose wealthy came indeed from commerce and banking rather than landholdings. Inspiring to neighbouring cities like Tivoli and Viterbo, also Rome's people began to think to a communal status and to a substantial freedom from papal authority.

Led by Giordano Pierleoni, Romans rebelled in 1143. The Senate and the Roman Republic were born again. Through the flaming words of preacher Arnaldo da Brescia, an idealistic, fierce opponent of ecclesiastical property and church interference in temporal affairs, the Commune of Rome continued until it was put down in 1155, though it left its mark on the civil rulership of the Eternal City for centuries. Twelfth -century Rome, however, had nothing to share with that which had ruled over the Mediterranean some 700 years before, and soon the new Senate had to work hard to survive, choosing an ambiguous policy of shifting its support from the Pope to the Holy Roman Empire and vice versa. At Monteporzio, in 1167, during one of these shifts, Roman troops were defeated by the imperial forces of Frederick Barbarossa. Luckily, the winning enemies were soon dispersed by a plague and Rome was saved.

In 1188 the new communal government was finally recognized by Pope Clement III. The pope had to make large cash payments to the communal officials, while the 56 senators became papal vassals. The Senate always had problems in the accomplishment of its function, and various changes were tried. Often a single senator was in charge. This sometimes led to tyrannies, which did not help the stability of the new-born organism.

In 1204 the streets of Rome were again in flames when the struggle between Pope Innocent III's family and its rivals, the powerful Orsini family, led to riots in the city. Many ancient buildings were then destroyed by machines used by the rival bands to besiege their enemies in the innumerable towers and strongholds which were a hallmark of the Middle Age Italian towns.

The struggle between the Popes and the emperor Frederick II, also king of Naples and Sicily, saw Rome support the Ghibellines. To repay his loyalty, Frederick sent to the commune the Carroccio he had won to the Lombards at the battle of Cortenuova in 1234, and which was exposed in the Campidoglio. In that year, during another revolt against the Pope, the Romans headed by senator Luca Savelli sacked the Lateran. Curiously, Savelli was the nephew of Pope Honorius III and father of Honorius IV, but in that age family ties often did not determine one's allegiance. Rome was never to evolve into an autonomous, stable reign, as happened to other communes like Florence, Siena or Milan. The endless struggles between noble families (Savelli, Orsini, Colonna, Annibaldi), the ambiguous position of the Popes, the haughtiness of a population which never abandoned the dreams of their splendid past but, at the same time, thought only of immediate advantage, and the weakness of the republican institutions always deprived the city of this possibility.

In an attempt to imitate more successful communes, in 1252 the people elected a foreign senator, the Bolognese Brancaleone degli Andal?. In order to bring peace in the city he suppressed the most powerful nobles (destroying some 140 towers), reorganized the working classes and issued a code of laws inspired by those of northern Italy. Brancaleone was a tough figure, but died in 1258 with almost nothing of his reforms turned into reality. Five years later Charles I of Anjou, then king of Naples, was elected senator. He entered the city only in 1265, but soon his presence was needed to face Conradin, the Hohenstaufen's heir who was coming to claim his family's rights over southern Italy, and left the city. After June 1265 Rome was again a democratic republic, electing Henry of Castille as senator. But Conradin and the Ghibelline party were crushed in the Battle of Tagliacozzo (1268), and therefore Rome fell again in the hands of Charles.

Nicholas III, a member of Orsini family was elected in 1277 and moved the seat of the Popes from the Lateran to the more defensible Vatican. He also ordered that no foreigner could become senator of Rome. Being a Roman himself, he had himself elected senator by the people. With this move, the city began again to side for the papal party. In 1285 Charles was again senator, but the Sicilian Vespers reduced his charisma, and the city was thenceforth free from his authority. The next senator was again a Roman, and again a pope, Honorius IV of the Savelli.