The Izu peninsula (伊豆半島, Izu-hantō) is a large mountainous peninsula with deeply indented coasts to the west of Tokyo on the Pacific coast of the island of Honshū, Japan. Formerly known as Izu Province, Izu peninsula is now a part of Shizuoka Prefecture. The peninsula has an area of 1,421.24 km2 (548.74 sq mi) and its estimated population in 2005 was 473,942 people. The populated areas primarily lie on the north and east.