The Principality of Brunswick-Wolfenbüttel was a subdivision of the Duchy of Brunswick-Lüneburg, whose history was characterised by numerous divisions and reunifications. It had an area of 3,828 square kilometres in the mid 17th century. Various dynastic lines of the House of Welf ruled Brunswick-Wolfenbüttel until the dissolution of the Holy Roman Empire in 1806. As a result of the Congress of Vienna, its successor state, the Duchy of Brunswick, was created in 1815.

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.