Vorderburg, Medieval castle ruin in Rüdesheim am Rhein, Germany.

Vorderburg, also called Marktburg, stands at the southwest edge of the market square in Rüdesheim's old town. Of the original castle only the nearly square defensive tower survives; around 1663 a dwelling house was built against it. The complex has been part of the UNESCO Upper Middle Rhine Valley World Heritage Site since 2002.

A noble family is first mentioned in 1189; the castle later passed to the Brömser von Rüdesheim. It was probably destroyed in 1640 by French soldiers, as was the Brömserburg. Only the nearly square keep survived, and around 1663 a dwelling was built against it.

The name Vorderburg, or Marktburg, refers to its position at the southwest edge of Rüdesheim's market square. The castle passed to the Brömser von Rüdesheim family, and the square keep that survives is the only remnant of the medieval fortification. Since 2002 the site has been part of the UNESCO Upper Middle Rhine Valley World Heritage.

The ruins are accessible via marked hiking trails that wind through vineyards with clear signposting to guide visitors. Sturdy footwear is recommended as the terrain is steep and uneven in places.

The near-square defensive tower is the only part of the medieval castle to survive; French soldiers destroyed the rest in 1640, as they did the nearby Brömserburg. Around 1663 a dwelling was built directly against the tower, so the present complex combines a 12th–13th-century fortification with a 17th-century house.