Blue zones are regions in the world where people are claimed to live longer than average. Examples of blue zones include Okinawa Prefecture, Japan; Nuoro Province, Sardinia, Italy; the Nicoya Peninsula, Costa Rica; and Icaria, Greece. The name "blue zones" derived simply during the original survey by scientists, who "used a blue pen on a map to mark the villages with long-lived population."

Okinawa Prefecture is the southernmost and westernmost prefecture of Japan. It has a population of 1,457,162 and a geographic area of 2,281 km2.