Albert the Tall (Latin: Albertus Longus, German: Albrecht der Große; 1236 – 15 August 1279), a member of the House of Welf, was Duke of Brunswick-Lüneburg from 1252 and the first ruler of the newly created Principality of Brunswick-Wolfenbüttel from 1269 until his death.
The Duchy of Brunswick and Lüneburg (German: Herzogtum Braunschweig und Lüneburg), commonly known as the Duchy of Brunswick-Lüneburg or Brunswick-Lüneburg, was an imperial principality of the Holy Roman Empire in the territory of present day Lower Saxony.
In 1235, Otto I was enfeoffed with the newly founded Duchy of Brunswick-Lüneburg at the Court of Mainz. It was based on the two castles in Brunswick and Lüneburg and the associated estate of the House of Welf. In 1269 there was a first division between the brothers Albrecht and Johann. The resulting principalities of Brunswick and Lüneburg together continued to form the Duchy of Brunswick-Lüneburg.