The Upper Harz Ditches (German: Oberharzer Gräben, pronounced [ˌoːbɐhaːɐ̯tsɐ ˈɡʁɛːbm̩]) are hillside ditches, running roughly parallel to the contour lines, that were laid out in the Upper Harz in Germany from the 16th to the 19th centuries to supply water power to the silver mines there. They are an important component of the Upper Harz Water Regale, a historical water system that is now a cultural monument.