Lummenfelsen der Insel Helgoland, Nature reserve at Heligoland, Germany.

Lummenfelsen on Heligoland is a protected area of red sandstone cliffs on the island's western side covering around 1 hectare. The vertical cliff faces provide nesting and roosting places for numerous seabird species that settle in rock crevices and ledges.

The area was designated a nature reserve by decree on 8 May 1964 (regulation No. 57/1964). It covers about 1.1 hectares, making it the smallest nature reserve in Schleswig-Holstein. Since 1980 or 1983 it has been managed mainly by volunteers from the Jordsand association, which monitors wildlife and runs information stands and guided tours.

The name comes from the guillemot (Trottellumme), called Lumme in German, which breeds on the cliffs. The reserve's Heligoland name is Skittenhörn. Since 1980 or 1983 the Jordsand association has supervised the area, and in one of the lobster huts (Hummerbuden) it provides information and regularly runs guided tours for visitors.

The reserve is reached via the Klippenrandweg on Heligoland's Oberland, where several viewpoints stand on the projecting rocks. The path and the rock shore at the foot of the cliffs are closed to the public. The Verein Jordsand, which has looked after the site since the 1980s, gives information in one of the Hummerbuden and runs regular guided walks.

The reserve covers only about 1.1 hectares, making it the smallest nature reserve in Schleswig-Holstein and one of the smallest in Germany, yet it holds the country's densest breeding-bird colony. The cliffs are the only German breeding site for the northern gannet, which first nested here in 1991 and reached around 420 pairs by 2009.