Tonowas, also known by its Spanish name of Dublon, is an island in the Chuuk (formerly Truk) lagoon, Federated States of Micronesia. It has an area of 8.8 km² and the population was 3,200 at the time of the last census (1980). A narrow single-lane track rings the island, allowing land access to the small settlements, two schools and Japanese military ruins, which include the remains of a seaplane anchorage and large fuel storage tanks.