The
Oshima Peninsula (渡島 半島
Oshima-hantō) is the
southernmost part of
Hokkaidō, the northernmost of the
Japanese islands. Where the peninsula starts is open to interpretation. A more generous interpretation is to draw a line southeast from Ishikari Bay across the Ishikari Plain to
Yufutsu. A narrower interpretation is to draw a line connecting
Suttsu on the
Sea of Japan and
Oshamambe on Uchiura Bay. This narrow interpretation encompases the
subprefectures of
Oshima and
Hiyama.