Balkan peninsula has 2 different meanings across 2 categories:
a large peninsula in southeastern Europe containing the Balkan Mountain Range
A large peninsula in southeastern Europe surrounded by water on three sides: the Adriatic Sea to the west, the Mediterranean Sea (including the Ionian and Aegean Seas) to the south and the Black Sea to the east. Its northern boundary is often given as the Danube, Sava and Kupa rivers.