The barbarian kingdoms were states founded by various non-Roman, primarily Germanic, peoples in Western Europe and North Africa following the collapse of the Western Roman Empire in the 5th century CE. The barbarian kingdoms were the principal governments in Western Europe in the Early Middle Ages. The time of the barbarian kingdoms is considered to have come to an end with Charlemagne's coronation as emperor in 800, though a handful of small Anglo-Saxon kingdoms persisted until being unified by Alfred the Great in 886.

The formation of the barbarian kingdoms was a complicated, gradual, and largely unintentional process. Their origin can be traced to the Roman state failing to handle barbarian migrants on the imperial borders, which led to both invasions and invitations into imperial territory from the 3rd century onwards. Despite an increasing influx of barbarians, the Romans simultaneously denied them the ability to properly integrate into the imperial framework. Barbarian rulers were at first local warlords and client kings without firm connections to any territory. Their influence only increased as Roman emperors and usurpers began to use them as pawns in civil wars. The barbarian realms only transitioned into proper territorial kingdoms after the collapse of effective Western Roman central authority.

Barbarian kings established legitimacy through connecting themselves to the Roman Empire. Virtually all barbarian rulers assumed the style dominus noster ("our lord"), previously used by Roman emperors, and many adopted the praenomen Flavius, borne by nearly all Roman emperors in late antiquity. Most rulers also assumed a subordinate position in diplomacy with the remaining Eastern Roman Empire. Many aspects of the late Roman administration survived under barbarian rule, though the old system gradually dissolved and disappeared, a process accelerated by periods of political turmoil.

"The barbarian kingdoms" is the collective term commonly used by modern historians to designate the kingdoms established in Western Europe after the collapse of the Western Roman Empire. The term has been criticized by some scholars on account of "barbarian" being a pejorative term. Some historians also consider "barbarian kingdoms" to be a misnomer since the kingdoms were supported and to a large degree staffed by former Roman elites. Alternate terms that have been proposed and used by some historians include "post-Roman kingdoms", "Roman-barbarian kingdoms", "Latin-Germanic kingdoms", "Latin-barbarian kingdoms", "western kingdoms", and "early medieval kingdoms".

"Barbarian kingdom" was not a contemporary term and was not used by the populace of the kingdoms to designate their own states. Early medieval writers in the kingdoms sometimes used "barbarian" in reference to denizens of other kingdoms, though never in reference to their own.

The rise of the barbarian kingdoms in the territory previously governed by the Western Roman Empire was a gradual, complex, and largely unintentional process. Their origin can ultimately be traced to the migrations of large numbers of barbarian (i.e. non-Roman) peoples into the territory of the Roman Empire. Although the Migration Period (c. 300–600) is often referred to as the "Barbarian Invasions", migrations were spurred not only by invasions but also by invitations. Inviting peoples from beyond the imperial frontier to settle Roman territory was not a new policy, and something that had been done several times by emperors in the past, mostly for economic, agricultural or military purposes. Because of the size and power of the Roman Empire, its capacity for immigration was nearly infinite. Several events through the fourth and fifth centuries complicated the situation.

Roman writers conceptualized these groups within long-standing ethnographic traditions that emphasized their cultural alterity. Descriptions of “barbarians” often owed more to literary convention than to direct observation, portraying them as uncivilized, warlike, and fundamentally distinct from Roman society. Such accounts functioned as tools of imperial ideology, justifying conquest and explaining Roman decline in moralizing terms. As historian Michael Maas observes, Roman ethnography at the end of antiquity was less concerned with the accuracy of description than with integrating these groups into narratives of Rome's fate and destiny.

While ethnographic stereotypes remained powerful, the formation of the kingdoms reflected pragmatic realities: federate armies carved out territories, imperial recognition was sometimes granted for political expediency, and Roman elites themselves often cooperated with new rulers. Scholars have debated whether the transition from tribal gentes to territorial regna marked the collapse of Rome or its transformation into a new political order.