The Quadi were a Germanic people during the Roman era, who were prominent in Greek and Roman records from about 20 AD to about 400 AD. By about 20 AD they had a kingdom centred in the area of present-day western Slovakia, north of the Roman border on the Danube river. After probably first settling near the Morava river the Quadi expanded their settlements eastwards over time until they also stretched into present day Hungary. This was part of the bigger region which had been partly vacated a generation earlier by the Celtic Boii. They were the easternmost of a series of four related Suebian kingdoms that established themselves near the river frontier after 9 BC, during a period of major Roman invasions into both western Germania to the northwest of it, and Pannonia to the south of it. The other three were the Hermunduri, Naristi (also known as Varisti), and the Quadi's powerful western neighbours the Marcomanni. Despite frequent difficulties with the Romans, the Quadi survived to become an important cultural bridge between the peoples of Germania to the north, the Roman Empire to the south, and the Sarmatian peoples who settled in the same period to their east in present day Hungary.
The Marcomannic wars, during the reign of the emperor Marcus Aurelius and his co-emperors, involved several rounds of particularly destructive conflict against the Quadi and their neighbours, who at one point even invaded Italy itself. By 180 AD when the emperor died on campaign in this region, there were new peace agreements between Rome and the Quadi, but these did not resolve the longer term problems which the region continued to face. Populations from more distant regions periodically disrupted the area. Small scale raiding from the neighbouring Sarmatian plain into Roman Pannonia continued, and this played a role in triggering more conflicts between the Quadi and Romans in the third and fourth centuries. However, while the original Marcomanni settlements in the northern Bohemian forest subsequently shrunk and became less important, the Quadi thrived near the Danube, and became more culturally integrated with both their Roman and Sarmatian neighbours.
Around 400 AD the Marcomanni and Quadi names suddenly disappeared from contemporary records. Since about 380 AD their Middle Danubian homelands had been dominated by peoples who had migrated from eastern Europe, most notably the Huns, Alans and Goths. In 395 AD however, Saint Jerome listed the Quadi and their neighbours the Sarmatians, Marcomanni, and Vandals, as peoples who had recently been ransacking the nearby Roman provinces together with the newcomers, the Goths, Alans and Huns. In 409 he placed the Quadi, Vandals, Sarmatians, Heruli, and even inhabitants of Roman Pannonia, in another list of peoples who had recently moved west and occupied parts of Gaul. These were the last clear contemporary records of the Quadi doing anything under their old name. Given their presence in Gaul in 409 AD the Quadi are considered likely to have been prominant among the Suevi who moved west into Iberia by 409 AD and founded the Kingdom of the Suebi in Gallaecia, in present day Spain and Portugal. This Gallaecian kingdom lasted for more than a century, until it was defeated by the Visigoths, and integrated into their kingdom in 585.
Meanwhile, until he died in 453, the empire of Attila controlled the Middle Danubian region. Smaller kingdoms were subsequently founded in or near the old Marcomanni and Quadi kingdoms, by the "Danube Suevi", as well as the Rugii, Heruli and Sciri. These "Danube Suevi" are likely to have included descendants of the Quadi, Marcomanni and other Suebian peoples of the region. Their short-lived independent kingdom was defeated by Ostrogoths at the Battle of Bolia in 469. Many of them apparently moved westwards under their king Hunimund, into present-day western Austria and southern Germany, where they became allies of the Alemanni. Other Quadi are presumed to have remained in the Middle Danube region and adapted to the subsequent waves of conquerors, either among the remaining settled communities, or among the more mobile groups which were prominent during this "migration period". Like their neighbours the Heruli, Rugii and Sciri, many probably became followers of the large forces which successfully invaded Italy from the Middle Danube under Odoacer (476), Theoderic the Great (493), and finally the Suebian Langobards (starting in 568), who are believed to have integrated Danubian Suebi into their ranks before moving into Italy.