Jizerské hory Protected Landscape Area, Protected mountain landscape in Liberecký kraj, Czech Republic.

The Isergebirge Protected Landscape Area covers 374 km² of the Jizera Mountains in the Liberec, Jablonec nad Nisou and Semily districts, rising from 317 m to the summit of Smrk at 1,124 m. Most of it lies on granite of the Krkonoše-Jizera pluton, with younger volcanic rocks at Bukovec and marble at Vápenný vrch. Long weathering has left many boulders and stone fields.

The Jizera Mountains Protected Landscape Area was declared in 1967, effective 1 January 1968, across parts of the Liberec, Jablonec nad Nisou and Semily districts, making it one of Czechia's oldest. At declaration, forests were damaged by emissions and fly ash from new coal-fired power plants on the German and Polish sides, then by forest pest outbreaks and heavy forestry mechanisation. Recovery began only after 1990, slowed by growing motorisation.

The area's name comes from the Jizera river, which flows through the mountains. The House of Nature in Oldřichov v Hájích serves as the visitor centre of the protected area, while its administration sits in Liberec. The beech forests of the Jizera Mountains were recognised in 1999 when seven separate reserves were merged into one national nature reserve.

The area is accessible for hiking and outdoor activities year-round with well-marked trails throughout the region. Winter brings groomed cross-country skiing routes, while summer offers mountain biking on established paths.

The highest point of the protected area is the summit of Smrk at 1,124 metres, while the lowest ground lies at 317 metres. The bedrock is mostly granite of the Krkonoše-Jizera pluton, and at Bukovec this granite is pierced by younger Tertiary volcanic rock.