As in many of the region’s towns, Oberwesel quite possibly had its beginnings as a Celtic settlement, named Vosavia or Volsolvia. The Romans later maintained a horse-changing station with a hostel here. After the fall of the limes, Oberwesel became a Frankish royal holding with a royal estate. The Wesel Estate passed under Emperor Otto I in 966 to the Archbishopric of Magdeburg. In 1220, Emperor Frederick II dissolved the pledge and Oberwesel became a free imperial city. In 1255, Oberwesel became a member of the Rhenish League of Towns (Rheinischer Städtebund), but in 1309, it lost its status as a free imperial city and fell under the lordship of the Electorate of Trier, to which it belonged until Secularization after the French Revolutionary Wars in 1802. In the so-called Weseler Krieg (“Wesel War”) in 1390 and 1391, the town tried yet again to turn over a new leaf, but after a successful siege by Archbishop of Trier Werner von Falkenstein, it had to back down.
Winegrowing, fishing, trade and handicrafts helped the town gather enough wealth to begin work on the town walls in 1220, building them in three phases from then until the mid 14th century. The town’s importance in the Middle Ages can be gathered from the two great ecclesiastical foundations that it harboured (Our Lady’s – or Liebfrauen in German – and Saint Martin’s), as well as the two monasteries and the Beginenhof. All together, nine monasteries had sizeable commercial holdings in town.