Istria (IS-tree-ë), Croatian and Slovenian Istra (IS-trah), Italian Istria (IS-tryah) is a peninsula in southern Slovenia and northwestern Croatia, in the north of the Adriatic Sea.

The name is derived from the Illyrian tribe of the Histri, which Strabo mentioned that lived in this region.

Important towns include Koper/Capodistria ("head of Istria"), Pula/Pola, Poreč/Parenzo, Rovinj/Rovigno, Pazin/Pisino, Labin/Albona, Motovun/Montona, Buzet/Pinguente and Buje/Buie. Of special mention are the tiny towns of Hum and Roč.

Most of Istria lies in Croatia today. It has a long tradition of tolerance between the people who live there, be it Croats, Italians, Slovenians, Serbs or anyone else. The Istrians are somewhat skeptical of official Zagreb and like their cultural autonomy.