William Thompson (1775 – 28 March 1833) was an Irish political and philosophical writer and social reformer, developing from utilitarianism into an early critic of capitalist exploitation whose ideas influenced the cooperative, trade union and Chartist movements as well as Karl Marx. Marxist James Connolly described him as the "first Irish socialist" and a forerunner to Marx, who cited Thompson in his works as well as being an influence upon Marx's thought.