Over the course of the 1st millennium BC the Greeks, Romans, and Carthaginians established colonies on the Mediterranean coast and the offshore islands. The Roman Republic annexed southern Gaul as the province of Gallia Narbonensis in the late 2nd century BC, and Roman forces under Julius Caesar conquered the rest of Gaul in the Gallic Wars of 58–51 BC. Afterwards a Gallo-Roman culture emerged and Gaul was increasingly integrated into the Roman Empire.
In the later stages of the Roman Empire, Gaul was subject to barbarian raids and migration, most importantly by the Germanic Franks. The Frankish king Clovis I united most of Gaul under his rule in the late 5th century, setting the stage for Frankish dominance in the region for hundreds of years. Frankish power reached its fullest extent under Charlemagne. The medieval Kingdom of France emerged from the western part of Charlemagne's Carolingian Empire, known as West Francia, and achieved increasing prominence under the rule of the House of Capet, founded by Hugh Capet in 987.
A succession crisis following the death of the last direct Capetian monarch in 1328 led to the series of conflicts known as the Hundred Years' War between the House of Valois and the House of Plantagenet. The war formally began in 1337 following Philip VI's attempt to seize the Duchy of Aquitaine from its hereditary holder, Edward III of England, the Plantagenet claimant to the French throne. Despite early Plantagenet victories, including the capture and ransom of John II of France, fortunes turned in favor of the Valois later in the war. Among the notable figures of the war was Joan of Arc, a French peasant girl who led French forces against the English, establishing herself as a national heroine. The war ended with a Valois victory in 1453.