Ong Iok-tek (王育德 pinyin: Wáng Yùdé; January 30, 1924–September 9, 1985) was a Taiwanese scholar and early leader of the Taiwan independence movement.

He was born in Tainan, of a prominent family. He attended Tokyo Imperial University in 1943 but World War II compelled him to returned to Taiwan after a year. He took a critical attitude toward the Kuomintang, one accentuated by the killing of his brother, a Tokyo-educated prosecutor, in the 228 Incident. His own life threatened by the new regime, he fled to Japan in 1949 and spent the rest of his life there.

He resumed his studies in 1950 and after completing his Ph.D. (1969) at the University of Tokyo, he taught Taiwanese at Meiji University (1974). He is still known as an authority on the language.

He also played a leading role in the Taiwan independence movement in Japan. As a student he had joined Liao Wenyi's Republic of Taiwan Provisional Government but became dissatisfied with it after two years. He established the Taiwan Youth Association in 1960 and published the organization's influential monthly Taiwan Seinen in Japanese (later for a time in Chinese) and Formosan Quarterly in English. The Taiwan Youth Association later changed its name to the Taiwan Youth Independence League. In the 1970s he was a leader in the campaign to secure compensation for the 200,000 Taiwanese who had served as soldiers under the Japanese. In 1982 he served as a committee member of the Formosan Association for Public Affairs .