The Social Democratic Front (SDF) is an opposition party of Cameroon currently led by Chairman Ni John Fru Ndi. It was launched in Bamenda on May 26: that day at least 6 people were killed when the security forces cracked down on peaceful demonstrators.

The party held its Constitutive Assembly on February 3, 1991 and elected its National Executive Committee. The SDF refused to sign the Tripartite Declaration of November 1991, and it chose to boycott the March 1992 parliamentary election, along with the Democratic Union of Cameroon, due to the government's failure to meet opposition demands, which included the establishment of an independent electoral commission to oversee the election.

The party took part in the presidential election in 1992 and its candidate John Fru Ndi received about 36% of the vote against about 40% for incumbent President Paul Biya, according to official results, however the SDF believes John Fru Ndi was denied victory "at gunpoint".

The SDF won 43 seats in the National Assembly in the May 1997 parliamentary election. It chose to boycott the October 1997 presidential election, along with the National Union for Democracy and Progress (UNDP) and the Cameroon Democratic Union (UDC). In the June 2002 parliamentary election, the SDF won 22 seats.

In the presidential election held on 11 October 2004, Fru Ndi stood again as the SDF candidate and won 17.4% of the vote according to official results. In the July 2007 parliamentary election, the SDF won 16 out of 180 seats. The SDF strongly opposed a constitutional amendment allowing Biya to run for president again in 2011. Its deputies boycotted the April 2008 parliamentary vote in which the amendment was approved, and it subsequently called for a "day of mourning" in which people were to wear black and stay home.