The Heruli (also Eluri, Eruli, Herules, Herulians) were one of the smaller Germanic peoples of Late Antiquity, known from records in the third to sixth centuries AD. The best recorded group of Heruli established a kingdom north of the Middle Danube, probably including the stretch where Vienna exists today. This kingdom was a neighbour to several other small and short-lived kingdoms in the late 5th century AD and early 6th century, including those of the Sciri, Rugii, Danubian Suebi, and Gepids. After the conquest of this Heruli kingdom by the Lombards in 508, splinter groups moved to Sweden, Ostrogothic Italy, and present-day Serbia, which was under Eastern Roman control.
The Danubian Heruli are believed to have originally moved from Ukraine during the late 3rd or early 4th century, where they are generally equated to the "Elouri", who lived near the Sea of Azov. In 267-270 they took part together with Goths and others in two massive raids into Roman provinces in the Balkans and Aegean Sea, attacking not only by land, but notably also by sea. The equation of these "ELuRi" with the "ERuLi" was made by several Byzantine authors, and is still widely accepted. However, some scholars such as Ellegård consider this uncertain, and have proposed that the Heruli homeland may have actually been elsewhere. For example, because a group of 6th century Heruli moved from the Danube to Scandinavia, some scholars believe that the Heruli had their earliest origins in Scandinavia. There are also proposals that there were Heruli kingdoms in several parts of Europe, already in the 3rd and 4th century, perhaps with common origins in the north. One proposal, based upon indirect evidence, is that there was a "Western Heruli" settlement based near the Lower Rhine. One reason for this is that in 286 AD, only a few years after the eastern raids, the Heruli were listed as one of the peoples who were defeated in Gaul trying to cross the Rhine.
Like the Goths, soon after first being noted in contemporary records as Eastern European raiders, Heruli also began entering the Roman empire and serving in its military, where they developed a particularly notable reputation already in the 4th century, at first mainly in the Western Roman Empire. A new Heruli unit was stationed in northern Italy. Heruli living near the Roman frontiers were among the many groups which caused disruption to the empire in this period. In 409 AD Heruli were among the "ferocious" nations that Saint Jerome described as occupying all of Roman Gaul. An important influence upon the movements of such peoples in this period was that the Huns were moving west. Eventually Attila's empire was based in the Danubian region. The Danubian Heruli kingdom known from later probably already existed in some form within this empire, as did the kingdoms of the Ostrogoths, Sciri, and Gepids.
After the death of Attila in 453, the Danubian Heruli fought in the Battle of Nedao in 454, although it is not certain which side they took among his various former allies. They also participated in successive conquests of Italy by Odoacer (476), Theoderic the Great (493), Narses (554), and probably also the Lombards (starting in 568). Under Roman command the Heruli played important military roles in Balkan, African, and Italian conflicts. With their last known kingdom in the Balkans eventually dominated by Rome however, and smaller groups integrated into larger political entities such as the Gepids and Lombards, the Heruli disappear from history around the time of the conquest of Italy by the Lombards. In this period the Middle Danube was coming under the control of the Pannonian Avars.