Henry Julius, a member of the House of Welf, was Duke of Brunswick-Lüneburg and ruling Prince of Brunswick-Wolfenbüttel from 1589 until his death. He also served as administrator of the Prince-Bishopric of Halberstadt from 1566 and of the Prince-Bishopric of Minden between 1582 and 1585.

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.