Ahrschleife bei Altenahr, Nature reserve in Altenahr, Germany.

Ahrschleife bei Altenahr is a 205-hectare nature reserve in the Langfigtal valley south of Altenahr. It contains the Ahr's largest meander loop, a three-kilometre bend where the difference between the steep outer bank and the gentle inner bank is clearly visible. The reserve is part of the Rhenish Slate Mountains, with steep slate outcrops and abandoned vineyard terraces.

The area was provisionally secured by regulation on 1 April 1980, amended on 9 March 1982, and designated a nature reserve on 14 October 1983 by the Koblenz regional government. Protection covers the river landscape and its rock formations as habitat for rare birds and plants. Floods on 14–15 July 2021 destroyed all footbridges in the Langfigtal and badly damaged the trail; the remains of the former open-air pool were removed in spring 2022.

The name Langfigtal refers to the narrow valley cut by the Ahr's largest meander loop. The slopes hold overgrown vineyard fallows whose dry-stone walls now shelter heat-loving animals and plants, remnants of former wine growing that visitors can still trace along the paths.

Several marked hiking trails cross the area and connect various viewpoints overlooking the river course. Sturdy footwear is recommended since paths go through wooded slopes and over elevated terrain.

The river bend is so pronounced that the Ahr forms an almost perfect loop when viewed from above, with only a few hundred meters of distance in some places between sections of the river. This extreme meander offers an unexpected display of river geography that becomes particularly clear from the higher trails.