Chlodio's successors are obscure figures, but what can be certain is that Childeric I, possibly his grandson, ruled a Salian kingdom from Tournai as a foederatus of the Romans. Childeric is chiefly important to history for bequeathing the Franks to his son Clovis, who began an effort to extend his authority over the other Frankish tribes and to expand their territorium south and west into Gaul. Clovis converted to Christianity and put himself on good terms with the powerful Church and with his Gallo-Roman subjects.

In a thirty-year reign (481–511) Clovis defeated the Roman general Syagrius and conquered the Kingdom of Soissons, defeated the Alemanni (Battle of Tolbiac, 496) and established Frankish hegemony over them. Clovis defeated the Visigoths (Battle of Vouillé, 507) and conquered all of their territory north of the Pyrenees save Septimania, and conquered the Bretons (according to Gregory of Tours) and made them vassals of Francia. He conquered most or all of the neighbouring Frankish tribes along the Rhine and incorporated them into his kingdom.

He also incorporated the various Roman military settlements (laeti) scattered over Gaul: the Saxons of Bessin, the Britons and the Alans of Armorica and Loire valley or the Taifals of Poitou to name a few prominent ones. By the end of his life, Clovis ruled all of Gaul save the Gothic province of Septimania and the Burgundian kingdom in the southeast.

The Merovingians were a hereditary monarchy. The Frankish kings adhered to the practice of partible inheritance: dividing their lands among their sons. Even when multiple Merovingian kings ruled, the kingdom—not unlike the late Roman Empire—was conceived of as a single realm ruled collectively by several kings and the turn of events could result in the reunification of the whole realm under a single king. The Merovingian kings ruled by divine right and their kingship was symbolised daily by their long hair and initially by their acclamation, which was carried out by raising the king on a shield in accordance with the ancient Germanic practice of electing a war-leader at an assembly of the warriors.