The Duchy of Jülich (; ; ) comprised a state within the Holy Roman Empire from the 11th to the 18th centuries. The duchy lay left of the Rhine river between the Electorate of Cologne in the east and the Duchy of Limburg in the west. It had territories on both sides of the river Rur, around its capital Jülich – the former Roman Iuliacum – in the lower Rhineland. The duchy amalgamated with the County of Berg beyond the Rhine in 1423, and from then on also became known as Jülich-Berg.