The Pannonian island mountains (Serbian: Панонске острвске планине / Panonske ostrvske planine, Croatian: Panonske otočne planine) 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: