Lothar Bisky (born 17 August 1941) is the chairman of the Party of Democratic Socialism, a socialist political party with its base in the east of Germany.

He lived in the former East Germany, and joined the Socialist Unity Party in 1963, but did not rise to leadership positions until shortly after the fall of communism and the resulting purge of hardliners from the party. He was rector of the University of Film and Television (Potsdam-Babelsberg) from 1986 to 1990. Since 1991 he has been on the board of directors of regional television channel ORB.

In 1990 he was a member of the Volkskammer and since 1990 he has been a member of the state parliament in Brandenburg.

He was chairman of the PDS from 1993 until his resignation in 2000 over a defeat for the executive committee on support for United Nations military intervention. He was re-elected chairman in 2003 after this "left turn" had cost the party its seats in the Bundestag in 2002. Bisky is seen to be on the moderate, social democratic wing of the party and he is a long-time close ally of the party's most prominent figure, Gregor Gysi.