The Mount Lofty Ranges are the range of mountains just to the east of Adelaide in South Australia.
The Mount Lofty Ranges stretch from the southernmost point of the Fleurieu Peninsula at Cape Jervis northwards for over 300 kilometres (190 mi) before petering out north of Peterborough. In the vicinity of Adelaide, they separate the Adelaide Plains from the extensive plains that surround the Murray River and stretch eastwards to Victoria.
The Heysen Trail traverses almost the entire length of the ranges, crossing westwards to the Flinders Ranges near Hallett.
The mountains have a Mediterranean climate with moderate rainfall brought by south-westerly winds, hot summers and cool winters. The southern ranges are wetter (with 900mm of rain per year) than the northern ranges (400mm).
The part of the ranges south of and including the Barossa Valley are commonly known as the South Mount Lofty Ranges, and the highest part of this section is the summit of Mount Lofty (727 m or 2,385 ft). The part of the ranges nearest Adelaide is also called the Adelaide Hills.
The ranges encompass a wide variety of land usage, including significant residential development, particularly concentrated in the foothills, suburbs of Stirling and Bridgewater, and the towns Mount Barker and Victor Harbor in particular. Several pine plantation forests exist, most significantly around Mount Crawford and Cudlee Creek in the north and Kuitpo Forest and Second Valley in the south. Several protected areas exist near Adelaide where the hills face the city in order to preserve highly sought-after residential land: Black Hill Conservation Park, Cleland Conservation Park and Belair National Park are the largest. The other significant parks in the southern ranges are Deep Creek Conservation Park, on the rugged southern shores of the Fleurieu Peninsula, and Para Wirra Conservation Park at the southern edge of the Barossa Valley.