Duchy of Brunswick-Lüneburg

The Duchy of Brunswick-Lüneburg (German: Herzogtum Braunschweig und 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.

The dukedom emerged in 1235 from the allodial lands of the House of Welf in Saxony and was granted as an imperial fief to Otto the Child, a grandson of Henry the Lion. The duchy was divided several times during the High Middle Ages amongst various lines of the House of Welf, but each ruler was styled "Duke of Brunswick-Lüneburg" in addition to his own particular title. By 1692, the territories had consolidated to two: the Electorate of Brunswick-Lüneburg (commonly known as the Electorate of Hanover), and the Principality of Brunswick-Wolfenbüttel.

In 1714, the Hanoverian branch of the family succeeded to the thrones of Great Britain and Ireland, which they ruled in personal union with Hanover until 1837. For this reason, many cities and provinces in former British colonies are named after Brunswick or Lüneburg. The Hanoverians never ruled Brunswick while they held the British throne, as the city was part of neighbouring Brunswick-Wolfenbüttel. After the Congress of Vienna in 1814/15, the Brunswick-Lüneburg territories became the Kingdom of Hanover and the Duchy of Brunswick.