The Illyrian deciduous forests form a terrestrial ecoregion of Europe according to both the WWF and Digital Map of European Ecological Regions by the European Environment Agency. It belongs to the biome of Mediterranean forests, woodlands, and scrub, and to the Palearctic ecozone.
The Illyrian deciduous forests stretch along the eastern coast of the Ionian and Adriatic Seas (including the islands) and occupy 40,600 km2 (15,700 sq mi) in Northern Greece, Albania, Montenegro, Bosnia and Herzegovina, Croatia, Slovenia and Northern Italy near Trieste.
The ecoregion is surrounded by the Aegean and Western Turkey sclerophyllous and mixed forests (in Greece), Pindus Mountains mixed forests (in Greece and Albania), Dinaric Mountains mixed forests (in Albania, Montenegro, Bosnia and Herzegovina, Croatia, Slovenia and Italy) and Po Basin mixed forests (in Italy).
Due to the wide altitudinal range of this ecoregion the highest elevations (above 1,000 m) are covered with conifer forests, with a mixed broadleaf vegetation and maquis shrubland occurring lower. The conifer zone is dominated by the Norway spruce, silver fir and European black pine with the admixture of the European beech. The dominant species of the lower zones include various deciduous oaks (Quercus frainetto, Q. pubescens, Q. cerris), Carpinus orientalis, Fraxinus ornus with Cotinus coggygria, Paliurus spina-christi, Cercis siliquastrum. Evergreen trees and maquis shrubs (Quercus ilex, Pinus halepensis, Pistacia terebinthus, P. lentiscus, Juniperus oxycedrus, J. macrocarpa, Arbutus unedo, A. andrachne, Nerium oleander) become predominant near the coast.
Phytogeographically, the ecoregion is shared between the Adriatic and East Mediterranean provinces of the Mediterranean Region within the Holarctic Kingdom (according to Armen Takhtajan's delineation).
- "Illyrian deciduous forests". Terrestrial Ecoregions. World Wildlife Fund.