Ljubljana Moor or Ljubljansko barje is a large wetland in the extreme south of the Ljubljana basin in the central part of Slovenia. It is a tectonic depression, with an extensive alluvial floor and flat surface, fringed by three major topographical regions: the Alpine foothills, carstic Dolenjska region and northern tip of carstified Dinaric mountains. Bottom can be generally divided into three basic topographic units, the most extensive being marshy flood-plain; then alluvial fans and finally isolated hills. Whole area is characterized by dynamic tectonic activity taking forms from long-term subsidence and uplift to catastrophic earthquakes, last one in 1895.

Main water-courses are Ljubljanica, Iščica and Iška with extensive carstic watersheds in Dinaric Mountains, and Gradaščica coming from Alpine foothills. Prior to the major regulation works and commercial peat extraction in the 19th century parts of the area were covered by up to 6 m thick peat blanket and characterised by a predictable cyclical annual floods nested within unpredictable cycle of major flood events. Today, as a result of flood control works, the landscape is effectively controllable and stable.