Stužica, National nature reserve in Snina District, Slovakia.

Stužica is a national nature reserve in the Bukovské vrchy mountains, in a deep valley around the Stužická rieka and its Kamenistý potok tributary, near the village of Nová Sedlica. It covers 761.49 hectares between 620 and 1,208 metres above sea level, protecting beech and fir-beech stands in every stage of forest development, with notably tall and old firs, beeches and sycamores.

Stužica was first protected in 1908. In 1965 it was declared a national nature reserve, with its status revised in 1974 and 1993 to cover 761.49 hectares. In 2007 the UNESCO World Heritage listing covered the larger Stužica–Bukovské Vrchy area of 2,950 hectares, not the reserve itself; five German components joined the site in 2011.

The name Stužica comes from the Stužická rieka, the stream that runs through the valley below Kremenec. The forest lies beside the Polish and Ukrainian borders near Nová Sedlica, and the Slovak reserve forms one continuous beech complex with Ukraine's Stužycia-Užok. The UNESCO listing covers 2,950 hectares, larger than the 761.49-hectare national reserve.

Access is via marked hiking trails starting from Nova Sedlica village, with a loop route covering about 19 kilometers. Visitors should bring sturdy hiking shoes and weather-resistant clothing, as the forest offers changing conditions across different elevations.

The forest contains trees at all stages of life, from young seedlings to specimens older than 200 years. This natural mixture shows how the woods regenerate on their own without human intervention.