The Grillenburg is a ruined medieval castle in Grillenberg in the district of Mansfeld-Südharz in the German state of Saxony-Anhalt.

The lower parts of the walls of the ruin, made of large rusticated ashlars, must date back to the original Romanesque fortification.

In 1347 the Margrave of Meißen, Frederick the Serious, purchased the estate back from the Duke of Brunswick who by then were the joint landlords together with the Margraviate of Landsberg.

The second phase of construction recognisable in the wall materials and characterised by brickwork is assessed by the sources as dating to the 14th century.

In 1547 on the death of George of Morungen the lordship fell as an expired fief to the Saxon district (Amt of Sangerhausen.