The United Democratic Front
) is an alliance of Centre to centre-left political parties in the Indian state of Kerala. It is one of the two major political alliances in Kerala, the other being CPI(M)-led LDF, each of which has been in power alternately for the last four decades. UDF has won elections to the State Legislature of Kerala in the years 1982, 1991, 2001, and 2011. The alliance currently acts as the main opposition in the state legislature of Kerala post-May 2016 election. The alliance consists of Indian National Congress, Indian Union Muslim League, Kerala Congress, Revolutionary Socialist Party, Forward Bloc and a variety of other smaller parties. The front follows the principle of Social democracy. It is a part of United Progressive Alliance at national level.