Ousmane Tanor Dieng (January 2, 1947 – July 15, 2019) was a Senegalese politician. He was the First Secretary of the Socialist Party of Senegal. He was vice-president of the Socialist International from 1996 until his death. Dieng was born in Nguéniène, Senegal. He was a candidate for President in the February 2007 election.