Socialist Democratic Party (SDP) or Malay: Parti Sosialis Demokratik was a splinter party of Democratic Action Party (DAP) formed in 1978 by Yeap Ghim Guan was later joined by Fan Yew Teng too after they left DAP because of their disappointment and dispute with the leadership of Lim Kit Siang. SDP failed to win any seat in the Malaysian general election, 1986 and it finally became defunct.