Rt. Hon. the Baroness Williams of Crosby is a British politician and academic. Originally a Labour Member of Parliament (MP) and Cabinet Minister, she left the party to help found the Social Democratic Party (SDP) in 1981. From 2001 to 2004, she served as Leader of the Liberal Democrats in the House of Lords, and served as Adviser on Nuclear Proliferation to Prime Minister Gordon Brown from 2007 to 2010. Baroness Williams also serves as Professor Emerita of Electoral Politics at the John F. Kennedy School of Government at Harvard University where she taught from 1988 to 2001. Baroness Williams has also served as Commissioner of the International Commission on Nuclear Non-Proliferation and Disarmament and as President of Cambridge Student Liberal Democrats.
She is currently a member of the Top Level Group of UK Parliamentarians for Multilateral Nuclear Disarmament and Non-Proliferation and is also a member of the Executive Board for the European Leadership Network (ELN).