Großsteingrab Alt Reddevitz, Neolithic dolmen in Vorpommern-Rügen District, Germany.

Großsteingrab Alt Reddevitz, also known as Herzogsgrab, is a Neolithic dolmen on the Mönchgut peninsula of Rügen. Its roughly 5.4-metre burial chamber is formed by four stones on each long side and closed by a larger stone to the north. A wind porch of two upright slabs stands at the south end; one six-tonne capstone survives intact, while two others are broken.

The dolmen, listed as Sprockhoff no. 509, was built between 3500 and 2800 BC by the Funnel Beaker Culture. Teacher and local poet Fritz Worm searched for it from 1920 after hearing a legend and found it in 1922 under shrubs and moss by the forest path between Alt Reddevitz and Göhren. Franz Klinghardt examined it in 1922–1924, and Greifswald University reopened the chamber around 1960, recovering pottery from at least 26 vessels, 22 flint axes and 56 arrowheads.

The name Herzogsgrab ("Duke's Grave") comes from a local legend that the teacher and dialect poet Fritz Worm from Alt Reddevitz heard around 1920; searching for the site it described, he found the overgrown tomb in 1922 on the forest path between Alt Reddevitz and Göhren. Excavations in 1922–1924 and again around 1960 uncovered around 40 individuals, cremation urns and grave goods.

The site is accessible through local roads and hiking paths departing from Middelhagen and remains open year-round for visitors. Being located in open countryside, sturdy footwear and weather protection are recommended, especially when conditions turn windy or wet.

The tomb's chamber is about 5.40 metres long, formed by four stones on each long side and closed by a larger stone to the north; a two-slab windbreak stands at the south end. One six-tonne capstone survives at its original size, while two others are broken into pieces. The finds, including pottery from at least 26 vessels and 56 arrowheads, are held by Greifswald University.