The Principality of Brunswick-Wolfenbüttel (German: Fürstentum Braunschweig-Wolfenbüttel) was a subdivision of the Duchy of Brunswick-Lüneburg, whose history was characterised by numerous divisions and reunifications.

After Otto the Child, grandchild of Henry the Lion, had been given the former allodial seat of his family (located in the area of present-day eastern Lower Saxony and northern Saxony-Anhalt) by Emperor Frederick II on 21 August 1235 as an imperial enfeoffment under the name of the Duchy of Brunswick-Lüneburg, the duchy was divided in 1267–1269 by his sons.

In a similar way, in 1432 the estates between the Deister hills and the Leine river, that had been gained in the meantime from the Middle House of Brunswick, split away to form the Principality of Calenberg.

The castle built here for the Brunswick-Lüneburg dukes—together with the ducal chancery, the consistory, the courts and the archives—became the nerve centre of a giant region, from which the Wolfenbüttel-Brunswick part of the overall duchy was ruled.

In the heyday of the town's development its districts were named after various dukes: the Auguststadt in the west, the Juliusstadt in the east and the Heinrichstadt.

Following the twelfth division of the duchy in 1495, whereby the Principality of Brunswick-Calenberg-Göttingen was re-divided into its component territories, Duke Henry the Elder was given the land of Brunswick, to which the name of the new Residenz at Wolfenbüttel was added.

In 1635 Duke Augustus the Younger, from the collateral line of Lüneburg-Dannenberg, took over the reins of power in the principality and founded the New House of Brunswick.

In 1671 an old pipe dream of the House of Welf dukes came true when the joint armies of the different dynastic lines were able to capture the town of Brunswick and add it to their domain.

In the process, the duke followed the trend and did not interfere with anything, including work on the new castle, begun in 1718 by Hermann Korb on the Grauer Hof which was still not finished.

Its southern edge was graced by the little Lustschloss of Antoinettenruh, built in 1733 instead of a garden house, a work by the master builder, Hermann Korb, who was so important to Wolfenbüttel.

In 1753 the teachers' training college was founded, which began in the orphanage and later moved to the building of the present-day Harztorwall School.

Numerous Brunswick-Wolfenbüttel officers served in high positions in the Prussian Army, most notably during the Seven Years' War.

During Charles I's era, there were great achievements in the cultural and scientific fields: the theatre was promoted and education encouraged.

In August 1784 Johann Wolfgang von Goethe stayed in Brunswick on a political mission, when he accompanied the Weimarsch minister, his duke, Charles Augustus.

As a result of the German Mediatisation of 25 February 1803 the principality was given the territories of the secularised imperial abbeys of Gandersheim and Helmstedt.

The recess laid down that all arbitrariness (Willkür) in the levies on stewards, or Meier, of feudal manors, particularly on the death of the farmer, were cancelled.