Philip I was on the French throne for 48 years, expanding the royal reign and courting controversy with neighboring countries and with the pope.

He was born in 1052 at Champagne-et-Fontaine. His father was King Henry I, and his mother was that king's second wife, Anne of Kiev. Henry crowned Philip as co-ruler in 1059, when the boy was just 7. When Henry died a year later, Philip ascended the throne but had a regent, his mother, and a co-regent, his uncle Baldwin V of Flanders.

Philip came of age in 1066 and set about ruling in his own name. He married Bertha of Frisia in 1072, and they had three children, one of whom died in infancy. Philip became enamored of another woman and, in 1090, decided that he no longer wanted to be married to Bertha. Instead, he took up with Bertrade de Montfort, who was married to someone else. Philip and Bertrade had three children.

The French bishop Hugh of Die in 1094 excommunicated Philip for these actions, and Pope Urban II did so as well a year later, at the Council of Clermont. Also at that gathering, the pope announced the First Crusade. Because Philip was technically banned from such endeavors, he did not participate in the expeditions to the Holy Land.

Philip expanded the royal domain, Ile-de-France, during his long reign, notably adding the county known as the Vexin in 1082 and the important city of Bourges in 1100. He also put down a number of revolts by nobles. He also intervened in political disputes in neighboring lands, such as Frisia and Normandy. Philip was one of the few who defeated William, Duke of Normandy on the field of battle, driving him from Brittany.

Philip spent the last few years of his life in painful obesity, which some historians attribute to a medical condition. He finally ended his battle with the papacy in 1107. By this time, he had named his son, Louis, as his co-ruler and successor. Philip died on July 29, 1108, and his son became Louis VI.