Kostrza nature reserve is a strict and forested nature reserve on Kostrza mountain in Beskid Wyspowy. It is located in Jodłownik and Limanowa commune – exactly in the area of Kostrza and Rupniów. It was appointed by the Governor of Małopolska (No. 5/2001) on 4 January, 2001. It is owned by the State Treasury and is subdivided into Limanowa Forest District. The reserve is located on the steep northern slopes of the mountain at 550 – 720 m above sea level and has an area of 38.56 hectares. It was created for the protection of well-preserved old trees and rare fern habitats. There are two forest groups in the reserve: Carpathian beech forest and sycamore (Lunario-Aceretum and Phyllitido-Aceretum). There are huge beeches which are about 150 years old. There are also protected plants like: ivy, Phyllitis scolopendrium, Asarum europaeum, Lilium martagon, Polypodium vulgare, Primula elatior, Glium odoratum. There are some mammals too: boar, roe deer and a hare. The area of this reserve was included in Natura 2000 sites.