The Lech is a river in Austria and Germany. It is a right tributary of the Danube 255 kilometres (158 mi) in length with a drainage basin of 3,919 square kilometres (1,513 sq mi). Its average discharge at the mouth is 115 m3/s (4,100 cu ft/s). Its source is located in the Austrian state of Vorarlberg, where the river rises from lake Formarinsee in the Alps at an altitude of 1,870 metres (6,120 ft). It flows in a north-north-easterly direction and crosses the German border, forming the Lechfall, a 12-metre-high (39 ft) waterfall; afterwards the river enters a narrow gorge. Leaving the Alps, it enters the plains of the Allgäu at Füssen at an elevation of 790 metres (2,580 ft) in the German state of Bavaria, where it used to be the location of the boundary with Swabia. The river runs through the city of Füssen and through the Forggensee, a man-made lake which is drained in winter. Here, it forms rapids and a waterfall.

Füssen is a town in Bavaria, Germany, in the district of Ostallgäu, situated one kilometre from the Austrian border. The town is known for violin manufacturing and as the closest transportation hub for the Neuschwanstein and Hohenschwangau castles. As of 2022-12-31, the town has a population of 15,985.