The Pierres Jumelles of Ecoivres (Mont-Saint-Eloi) are megalithic monuments in the Pas-de-Calais department in France. They are two cone-shaped sandstone menhirs, 3 meters and 3.80 meters high respectively, which were erected about 5,000 years ago. The stones are located near the hamlet of Écoivres, in the municipality of Mont-Saint-Éloi. The stones are also called Pierres du Diable, Pierres d'Acq, Demoiselles or Demoiselles d'Acq. The stones have been classified as historical monuments since 1889. There are several legends about the origin of these stones, one of which claims that the stones were made by the devil.