Her father was Boniface, marquis of Tuscany and count of Reggio, Modena, Mantua, Brescia, and Ferrara. As this string of titles implies, he held a great estate on both sides of the Apennines, though the greater part was on the Lombardy side.
Her mother was Beatrice of Lorraine, a daughter of Frederick II, duke of Upper Lorraine, and of Matilda of Swabia.
Matilda was her parents' youngest child, but her father was murdered in 1052, and her older sister and brother died soon afterwards, leaving the eight-year-old Matilda as a great heiress under her mother's guardianship. Two years later Beatrice re-married, in part to protect her daughter's inheritance, to Godfrey the Bearded, a cousin who had been duke of Upper Lorraine before rebelling against Emperor Henry III.
Matilda's family became heavily involved in the series of disputed papal elections of the last half of the 11th century. Her stepfather's brother Frederick became Pope Stephen IX, while both of the following two popes, Nicholas II and Alexander II had been Tuscan bishops. Her parents' forces were used to protect these popes and fight against anti-popes. Some stories claim the adolescent Matilda took the field in some of these engagements, but no evidence supports this.
Sometime in this period Matilda married her stepbrother Godfrey the Hunchback, son of Godfrey the Bearded's first marriage. The two became estranged after Godfrey the Bearded's death in 1069, and he returned to Germany, where he eventually received the duchy of Lower Lorraine.
Both Matilda's mother and husband died in 1076, leaving her in sole control of her great Italian patrimony as well as lands in Lorraine, while at the same time matters in the conflict between Pope Gregory IV and the German king Henry IV were at a crisis point. Pope had excommunicated King, causing a weakening of Henry's German support and motivating him to cross the Alps during that winter, and appear early in 1077 as a barefoot penitent in the snow before the gates of Matilda's ancestral castle of Canossa, where the pope was staying.
This famous meeting did not settle matters for long. In 1080 Henry was excommunicated again, and the next year he crossed the Alps, aiming either to get the pope to end the excommunication and crown him emperor, or to depose the pope in favor of someone more co-operative.
Matilda controlled all the western passages over the Apennines, forcing Henry to approach Rome via Ravenna. Even with this route open, he would have difficulties besieging Rome with a hostile territory at his back. Some of his allies defeated her at Volta (near Modena) in October 1080, and by December the citizens of Lucca, then the capital of Tuscany, had revolted and driven out her ally Bishop Anselm.
In 1081 Matilda sufferred some further losses, and Henry formally deposed her in July. But this was not enough to eliminate her as a source of trouble. She remained as Pope Gregory's chief intermediary for communication with northern Europe, even as he lost control of Rome and holed up in the Castel Sant' Angelo. After Henry had obtained the Pope's seal, she wrote to supporters in Germany only to trust papal messages that came though her.
Henry's control of Rome enabled him to have his choice of pope, Antipope Clement III, consecrated and in turn for this pope to crown Henry as emperor. That done, Henry returned to Germany, leaving it to his allies to attempt Matilda's dispossesion. These attempts foundered after Matilda routed them at Sobara (near Modena) on July 2, 1084.
Gregory VII died in 1085, and Matilda's forces once again took the field in support of a new pope, Victor III.
Sometime around 1090 Matilda married again, to Welf V of Bavaria, from a family (the Welfs) whose very name was later to become synomynous with alliance to the popes in their conflict with the German emperors (see Guelphs and Ghibellines). This forced Henry to return to Italy, where he drove Matilda into the mountains. But again he was humbled before Canossa, this time in a military defeat in October 1092, from which his influence in Italy never recovered.
Matilda's death of gout in 1114 marked the end of an era in Italian politics. She had no heirs and left her allodial property to the Pope, while Henry had promised some of the cities in her territory he would appoint no successor after he deposed her. In her place the leading citizens of these cities took control, and we enter the era of the city-states in northern Italy.
In the 17th century her body was removed to the Vatican, where it now lies in St. Peter's Basilica.
The story of Matilda and Henry IV featured in Luigi Pirandello's play Enrico IV.