Japan’s smallest main island still means “four provinces”
Shikoku—literally “four provinces”—is Japan’s smallest and least populated main island, about 225 kilometres long and 50–150 wide, with roughly 3.5 million residents across Ehime, Kagawa, Kōchi, and Tokushima. The island group covers about 18,800 square kilometres, ranking fiftieth globally by area.
Mountains running east to west split the island in two: a crowded strip facing the Seto Inland Sea in the north and a larger, thinly settled Pacific side in the south. Nearly all the big cities lie in the north; Matsuyama, capital of Ehime, is the largest with about 507,000 people. In the south the only real lowland is the small alluvial plain around Kōchi, where mild winters allow out-of-season vegetables under plastic and two rice harvests a year, and paper mills have drawn on the forests and hydroelectric power.
The Yoshino River runs 196 kilometres from near Mount Ishizuchi to Tokushima city and is well known for white-water rafting. Four capes mark the extremities: Gamōda in the east, Sada in the west, and Muroto and Ashizuri jutting into the Pacific, with Ashizuri the southern tip; the northernmost point lies in Takamatsu. Ashizuri-Uwakai National Park covers the south-west.
Unlike Japan’s other three main islands, Shikoku has no active volcanoes, the largest Japanese island without any. A great caldera near Mount Ishizuchi was active in the Miocene, about 14 million years ago, and the small cone of Mount Iino erupted at some unknown date.
The population was 3,486,739 in 2025, a density of about 193 per square kilometre, third among the main islands. Numbers peaked in 1953 and have fallen from 1950 to 1970 and again since 1990. Long isolation preserved older Japanese plant life and building methods, and the island is dotted with Buddhist temples. The American writer Alex Kerr lived for years from 1970 in a remote village near Oboke and described this lost Shikoku.
Source: Shikoku
