The first United Democratic Party (1995-1997) was a moderate liberal party. It broke away from Kim Dae-jung's Democratic Party/National Congress for New Politics. Its members included future president Roh Moo-hyun. In 1997, it merged with the New Korea Party to form the Grand National Party.

The second United Democratic Party (2008) served as the country's main liberal opposition party. It was formed by the merger of the United New Democratic Party and the Democratic Party. It participated in the 2008 parliamentary elections and shortly after changed its name to simply the Democratic Party.