The Okinawa Urban Monorail , also known as Yui Rail , is a monorail line serving the cities of Naha and Urasoe, Okinawa, Japan. Operated by Okinawa Urban Monorail, Inc. , it opened on 10 August 2003, and is the only public rail system in Okinawa Prefecture. Yui Rail is the first rail line on Okinawa since World War II. As Okinawa is the island of Japan lying farthest to the south and west that has an active rail line, Akamine Station and Naha Airport Station, the southernmost and westernmost rail stations in Japan respectively, lie on this line. It uses the OKICA as its contactless smart card, and integrates with Suica and other major Japanese IC cards from 10 March 2020.

Naha is the capital city of Okinawa Prefecture, the southernmost prefecture of Japan. As of 1 June 2019, the city has an estimated population of 317,405 and a population density of 7,939 persons per km2. The total area is 39.98 km2 (15.44 sq mi).