Burg Bornstedt, Medieval castle in Bornstedt, Germany.

Burg Bornstedt, also known as Schweinsburg, is a medieval castle ruin in Saxony-Anhalt that stands on elevated ground. The remaining outer walls demonstrate how fortifications of this period were built and laid out.

Burg Bornstedt was recorded around 880 as "Brunstediburg" in the Hersfeld tithe register and was probably an imperial castle or fortified settlement as early as the 8th century. In 1115 Emperor Henry V stationed troops there during the fighting at the Welfesholz against the Saxons. From 1120 the castle gave its name to Esico II, dominus castri Burnstede. From 1301 to 1780 it belonged to the Counts of Mansfeld, and decay began in 1615.

The ruins display features of medieval fortification design that remain visible in the preserved walls today. Visitors can observe how defensive structures of this era were constructed by examining the stonework.

The site is best reached from the village of Bornstedt, which sits in the surrounding area. Visitors should be prepared for uneven ground and potential hazards when exploring the ruins.

The name Schweinsburg, or Schweinsberg, comes from a siege anecdote: the defenders spared their last pig and made it squeal loudly several times a day, suggesting they slaughtered many pigs and had ample supplies. The attackers gave up the siege. The castle area measured 350 by 200 metres.