Julius of Brunswick-Lüneburg, a member of the House of Welf, was Duke of Brunswick-Lüneburg and ruling Prince of Brunswick-Wolfenbüttel from 1568 until his death. From 1584, he also ruled over the Principality of Calenberg. By embracing the Protestant Reformation, establishing the University of Helmstedt, and introducing a series of administrative reforms, Julius was one of the most important Brunswick dukes in the early modern era.

The Duchy of Brunswick-Lüneburg, or more properly the Duchy of Brunswick and Lüneburg, was a historical duchy that existed from the late Middle Ages to the Late Modern era within the Holy Roman Empire, until the year of its dissolution. The duchy was located in what is now northwestern Germany. Its name came from the two largest cities in the territory: Brunswick and Lüneburg.