The kingdom of Tamna or Tamna guk ruled Jeju Island from ancient times until it was absorbed by the Korean Joseon Dynasty in 1404. This kingdom is also sometimes known as Tangna (탁라), Seomna (섭나), and Tammora (탐모라). All of these names mean "island country".

There is no historical record of the founding or early history of Tamna. One legend tells that the three divine founders of the country—Ko (고), Yang (양), and Bu (부)—emerged from three holes in the ground in the 24th century BC. These holes, known as the Samseonghyeol (삼성혈), are still preserved in Jeju City.

According to legend, after Yang Ul-la (양을나/良乙那; modern-day 楊乙那) came to Jeju Island, a semi-mythical box washed up on the shore of the island. Yang Ul-la searched in the box and found three women, horses, cows, and agricultural seeds such as rice, corn, grain, millet, barley, and bamboo. From these beginnings, the three men established the kingdom of Tamna. He is regarded as the legendary ancestor of Yang Tang, the founder of the Jeju Yang bon-gwan.

Archaeological evidence indicates that the people of Tamna were engaging in active trade with Han Dynasty China and Yayoi Japan, South-east-asian nations, with the Tamil Chola dynasty, as well as mainland Korea, by the 1st century AD. The first historical reference to the kingdom may come in the 3rd century AD, in the chronicle of the Chinese Three Kingdoms period called the Sanguozhi. The Sanguozhi reports a strange people living on a large island near Korea, which it calls Juho (州胡, literally "island barbarians"). These people, who had a distinctive language and culture, engaged in trade with the Mahan people of the mainland. However, the identity of Juho with Tamna has been disputed by authorities such as the North Korean scholar Yi Jirin (이지린), who claims that Juho was a small island in the Yellow Sea. Tamna is pronounced Dānluó (Wade-Giles: Tan¹-luo²) in Standard Mandarin Chinese.

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