Älvsjöskogen, Nature reserve in Södermanland, Sweden

Älvsjöskogen is a nature reserve in Södermanland featuring steep hillsides and distinctive fissure valleys carved into the landscape. The forest grows naturally with fallen trees scattered throughout, creating habitats for a wide range of wildlife.

In 1998 Stockholm's municipal council tasked its planning and property offices with protecting all of Älvsjöskogen as a nature reserve, a process complicated by the Swedish Church's ownership of part of the land. In December 2015 the city council decided to make the western part a reserve; the eastern part, Hagsätraskogens nature reserve, followed in 2021. In late 2009 local villa associations stopped a planned row-house development near the road Korkskruven.

The old Göta landsväg ran along the western edge, from the Viking Age until the 17th century Stockholm's only land route south to the continent. The forest keeps the marks of peasant use: selective felling for household needs and grazing cattle that kept it more open, as the old deciduous trees now crowded by spruce show. On dead birches, look for the hoof fungus (Fomes fomentarius), whose tinder was once used to start fires.

Marked trails of varying difficulty guide visitors through the forest at their own pace and level of fitness. Picnic areas and rest spots are provided along the pathways.

Alkärret, a bog pool in the forest, is the single most populous breeding site for the common frog within Stockholm municipality. Since 2003 the action group "Rädda Långsjöns grodor" has organised residents of Herrängen and Långsjö to help thousands of frogs cross safely on their migration to Långsjön. Look also for the black woodpecker's feeding holes in spruce trunks, chiselled to the core in search of horse ants.