William Thomas Rodgers, Baron Rodgers of Quarry Bank, PC (born 1928), usually known as William Rodgers but also often known as Bill Rodgers, was one of the "Gang of Four" of senior British Labour Party politicians who defected to form the Social Democratic Party (or SDP). He subsequently helped to lead the SDP into the merger that formed the Liberal Democrats, and later served as that party's leader in the House of Lords.

Rodgers first entered the British House of Commons in 1962, and served in Labour Governments under Harold Wilson and James Callaghan, becoming Secretary of State for Transport in Callaghan's Cabinet in 1976. He held the post until Labour's defeat in the 1979 general election. With Labour drifting to the left, Rodgers joined Shirley Williams, Roy Jenkins and David Owen in forming the Social Democratic Party in 1981.

At the 1983 general election the SDP-Liberal Alliance won many votes but few seats, and Rodgers lost his seat of Stockton North (known as Stockton-on-Tees before the boundary changes of 1983). He remained outside Parliament, unsucessfully contesting Milton Keynes for the SDP in the 1987 general election, until he recieved a life peerage in 1992. During that interval he was Director-General of the Royal Institute of British Architects and also became Chairman of the Advertising Standards Agency .

In 1987 Rodgers was chairman of the successful "Yes to Unity" campaign within the SDP in favour of merger with the Liberal Party. He became the Liberal Democrats' Lords spokesman on Home Affairs in 1994 and was its leader in the Lords between 1997 and 2001. His autobiography was titled Fourth Among Equals, reflecting his position as the least prominent of the SDP's founders.