A truncated spur is a landform that occurs in glaciated areas. It is a spur, which is a ridge that descends towards a valley floor or coastline from a higher elevation, that ends in an inverted-V face and was produced by the erosional truncation of the spur by the action of either streams, waves, or glaciers. Truncated spurs can be found within mountain ranges, along the walls of river valleys, or along coastlines.

Before glaciation, relatively immature rivers display a pattern of interlocking spurs. A valley glacier cannot avoid the interlocking spurs as a river can. As the valley glacier moves, abrasion and plucking erode the protruding tips of the spurs, leaving steep cliff-like truncated spurs. Hanging valleys are found in between truncated spurs as they join the main glacial valley from the side. It is common for waterfalls to form from them, where they fall into the main valley.

Truncated spurs are often rounded at the top but steep at the bottom. They are found in between hanging valleys and are the inverted "v" shape where the former tributary valleys have been sliced off by a lower valley glacier. The landform is the result of mainly vertical glacier erosion and is a steep bluff on the side of a glacial trough, protruding between tributary, possibly hanging, valleys.