Weißenfels is the largest town of the Burgenlandkreis district, in southern Saxony-Anhalt, Germany. It is situated on the river Saale, approximately 30 km (20 mi) south of Halle.

Perhaps the first mention of the area, before the town itself was founded occurred in 806 CE, when Charles the Younger, King of the Franks, fought and killed two West Slavic Knezy (princes) nearby: duke Miliduch of the Sorbs and Nessyta (possibly also a Sorbian leader). Miliduch had led a Sorbian invasion of Austrasia.

The settlement arose around a castle on a ford crossing the Saale and received municipal rights in 1185. During the Thirty Years' War, the town was badly damaged and the population fell from 2200 to 960. On 7 November 1632 the body of King Gustavus Adolphus of Sweden was first laid out at Weißenfels after he had been killed the day before at the Battle of Lützen.

Shortly afterwards however, the town took a steep rise in importance, when Duke Augustus, a scion of the Saxon House of Wettin, established the Duchy of Saxe-Weissenfels in 1656 and chose Weißenfels as his residence and as the capital of the duchy. Since 1638 Augustus had served as the Protestant administrator of the Magdeburg archbishopric, which, according to the 1648 Peace of Westphalia would be finally secularised to Brandenburg-Prussia upon his death.

Augustus therefore from 1660 onward erected the Baroque Neu-Augustusburg Castle on a hill in Weißenfels as the seat of his ducal successors. Completed in 1680 it became the duchy's administrative as well as cultural centre until its dissolution in 1746. Composers like Johann Philipp Krieger and Georg Philipp Telemann worked here, the actress Friederike Caroline Neuber made her first appearances at Weißenfels. In 1702 Johann Sebastian Bach's application for the position of the organist in Sangerhausen failed, because the Duke of Saxe-Weissenfels preferred the—rediscovered in 2010-composer Johann Augustin Kobelius. In 1713 Johann Sebastian Bach dedicated his cantata Was mir behagt, ist nur die muntre Jagd, BWV 208 to Duke Christian of Saxe-Weissenfels.

The Lutheran theologian Erdmann Neumeister from 1704 on served as a deacon at the ducal palace's Trinity Chapel. Its pipe organ completed in 1673 has 22 stops. According to John Mainwaring, Duke Johann Adolf I of Saxe-Weissenfels himself discovered the musical talent of George Frideric Handel, when he heard the son of his physician Georg Händel playing on the organ. Bach wrote the Toccata and Fugue in F major (BWV 540) for it.

With the extinction of the Wettin Saxe-Weissenfels line in 1746, the town fell back to the Saxon Electorate and after the 1815 Congress of Vienna to the Prussian Province of Saxony. From 1816 on it was the capital of the Weißenfels district until its dissolution in 2007.