Castle Thorun, Medieval castle ruins on Burgwartsberg near Dresden, Germany.

Castle Thorun is a castle ruin located on a strategic hilltop called Burgwartsberg near Dresden. The stone foundations that remain reveal how the medieval structure was positioned to survey the Weißeritz valley and surrounding lands below.

Burg Thorun appears in a single 1206 charter, in which its demolition was ordered. The document records a legal dispute between the Bishop of Meißen and the burgraves of Dohna, settled by Margrave Dietrich the Oppressed, who ordered the castle destroyed and began building his own Tharandt castle nearby the same year. The charter is held to be the first written mention of Dresden and of several districts of present-day Freital.

The founding document of this castle provided the first written record of Dresden and several districts of Freital. This paperwork shaped how these places were recognized and remembered in the region's early history.

A marked hiking path leads to the ruins and an information board that explains the medieval structure. Visitors should wear sturdy footwear since the ground is hilly and can be uneven in places.

Reinhard Spehr links the name to Toron, a Crusader castle in the Holy Land: the Dohna burgrave took part in the crusade of Emperor Henry VI and built Thorun around 1200/01 after his return. Other researchers date the site to around or soon after 1190.