Harold John Blackham was a leading British humanist and writer on philosophical and historical subjects.
Joining the Ethical Union, Blackham drew the organisation further away from religious forms and played an important part in its formation into the British Humanist Association, becoming the BHA's first Executive Director in 1963. He was also a founding member of the International Humanist and Ethical Union, IHEU secretary, and received the IHEU's International Humanist Award in 1974, and the Special Award for Service to World Humanism in 1978. In addition he was one of the signers of the Humanist Manifesto.
His book Six Existentialist Thinkers became a popular university textbook.
He died on 23 January 2009 at the age of 105.