Heidelberg Castle (German: Heidelberger Schloss) is a ruin in Germany and a landmark of Heidelberg. The castle ruins are among the most important Renaissance structures north of the Alps.

The castle has only been partially rebuilt since its demolition in the 17th and 18th centuries. It is located 80 metres (260 ft) up the northern part of the Königstuhl hillside and thereby dominates the view of the old downtown. It is served by an intermediate station on the Heidelberger Bergbahn funicular railway that runs from Heidelberg's Kornmarkt to the summit of the Königstuhl.

The earliest castle structure was built before 1214 and later expanded into two castles circa 1294; however, in 1537, a lightning-bolt destroyed the upper castle. The present structures had been expanded by 1650, before damage by later wars and fires. In 1764, another lightning bolt caused a fire which destroyed some rebuilt sections.