Graham Watson was born in Scotland. He first became active in the liberal movement joining the Scottish Young Liberals and the Scottish Liberal Party. Watson represented both parties in umbrella organisations such as the European Federation of Liberal and Radical Youth (EFLRY), renamed in 1979 the International Federation of Liberal and Radical Youth (IFLRY), the Liberal and Radical Youth Movement of the European Community (LYMEC) and the British Youth Council.
Graham Watson later moved to Langport, England and became active in the British Group of the Liberal International. He was a MEP for the Somerset and North Devon Constituency, later renamed the South West England Constituency in 1999, and expanded to include Gibraltar in 2004, from 1994 - 2014. Watson served as Chair of LIBE Committee from 1999-2001. Following this, from 2002–2009, he served as President of the European Liberal Democrat and Reform Party (ELDR), and from 2011-2015 was President of the Alliance of Liberals and Democrats for Europe Party (ALDE).
Watson was a leading voice in the regional ‘Bremain’ campaign during the United Kingdom European Union membership referendum, 2016. He was knighted in the 2011 Birthday Honours for political and public service. He is also the Honorary President and co-founder of the Climate Parliament.