The Pannonian island mountains (, ) is a term for isolated mountains scattered across the Pannonian Plain, chiefly its western and southern parts, in Hungary, Serbia and Croatia. In prehistoric times, these mountains were islands of the ancient Pannonian Sea that disappeared about 600,000 years ago.
The island mountains include: Croatia Central Slavonian Mountains: Dilj Krndija Papuk Psunj Požeška Gora Medvednica in western Croatia
Hungary
Transdanubian Mountains of western Hungary: Bakony Buda Hills Gerecse Pilis Mountains Vértes Hills Velence Mountains Mecsek, in south Hungary Kőszeg Mountains (Geschriebenstein), on Hungary–Austria border Baranya Hills
Serbia (autonomous province of Vojvodina) Fruška Gora Vršac Mountains