former duchy of the Holy Roman Empire, centred on the town of Jülich, located now in the Aachen district of the Land (state) of North Rhine-Westphalia, Germany.

The counts of Jülich inherited or were enfeoffed with most of the lands of the Rhenish Palatinate north of the Eifel Mountains, including control of the imperial city of Aachen, as a result of their support for the Hohenstaufen emperors in the 12th and 13th centuries. William V of Jülich, through his marriage in 1328 to the daughter of Count William III of Holland, became the brother-in-law of Emperor Louis IV, who made Jülich a margravate in 1336, and of Edward III of England, whom he helped to secure an alliance with German princes at the outbreak of the Hundred Years' War. He was also active in the affairs of Holland, extended his territory northward, and acquired ducal rank as William I in 1356 and the hereditary office of marshal of the empire.

In 1423 Jülich was united with Berg and Ravensberg. In 1511 the duchies passed to John III, duke of Cleves (died 1539). John's son, William V the Rich (died 1592), as duke of Cleves-Jülich-Berg, directed the Netherlands-Westphalian circle (Kreis) of the Holy Roman Empire. When William's successor, John William, died childless in 1609, John Sigismund, elector of Brandenburg, and Wolfgang William of Palatinate-Neuburg, backed by France, the United Provinces, and the German Protestant princes, jointly occupied the duchies (1610). By the Treaty of Xanten (1614), they agreed to a division of the territories. Cleves-Mark and Ravensberg went to John Sigismund, Jülich-Berg and Ravensstein, to Wolfgang William.

Jülich-Berg was inherited by Charles Theodore of Palatinate-Sulzbach (who later became elector of Bavaria). Jülich was absorbed into France during the Napoleonic era; Berg at the same time was made a grand duchy and a member of the Confederation of the Rhine. The whole region became part of Prussia's Rhine province by award of the Congress of Vienna in 1815.