Gongju (Gongju-si), also spelt Kongju, is a city in South Chungcheong province, South Korea.

Gongju was formerly named Ungjin and was the capital of Baekje from AD 475 to 538. In this period, Baekje was under threat from Goguryeo. Goguryeo had overrun the previous capital of Hanseong (modern-day Seoul), which forced Baekje to find a new center of strength.

In 538, King Seong moved the capital to Sabi (in modern-day Buyeo County). However, Gongju remained an important center until the kingdom's fall in 660.

On August 11, 2004, the South Korean Prime Minister Lee Hae-chan announced that the country's capital will be moved from Seoul to Gongju (approximately 120 km south of Seoul) and Yeongi commencing in 2007. A 72.91 square kilometres (18,020 acres) site was chosen for the project, which was scheduled to be completed by 2030. It was envisaged that government and administrative functions will move to the new capital, along with (possibly) the National Assembly and supreme court, although no sizable relocation was expected until the first phase of the project has been completed by 2012.