Ulleungdo is a South Korean island 120 km east of the Korean Peninsula, formerly known as the Dagelet Island or Argonaut Island in Europe, and known as Yùlíng-dǎo in Chinese and Utsuryō-tō in Japanese.
Volcanic in origin, the rocky steep-sided island is the top of a large stratovolcano which rises from the seafloor, reaching a maximum elevation of 984 metres at Seonginbong Peak. The island is 9.5 kilometres in length and 10 kilometres in width; it has an area of 72.86 km². It has a population of 10,426 inhabitants.
The island makes up the main part of Ulleung County, North Gyeongsang Province, South Korea and is a popular tourist destination. The main city of Ulleung-do is the port of Dodong, which serves as the main ferry port between Ulleung-do and the South Korean mainland. After tourism, the main economic activity is fishing, including its well-known harvest of squid, which can be seen drying in the sun in many places.