Suevi, collective name for a number of German tribes (including the Marcomanni and Lombards), mentioned in the 1st century bc by Julius Caesar as dwelling east of the Rhine River. The Roman historian Cornelius Tacitus described (1st century ad) them as inhabiting all central Germany. One group of Suevi allied themselves with the Vandals and the Alans and swept down on the Iberian Peninsula in ad407. By 411 they were established in northern Portugal and Galicia and by 452 in Castile. They adopted Catholic Christianity and ruled until the end of the 6th century when they were finally subjugated by the Visigoths. The Suevi who remained in Germany are the ancestors of the medieval Swabians. The name is also spelled Suebi.