Sir Isaiah Berlin OM (6 June 1909 – 5 November 1997) was a Russian-British philosopher and historian of ideas, regarded as one of the leading thinkers of the twentieth century, and as the dominant liberal scholar of his generation. He excelled as an essayist, conversationalist and raconteur; and as a brilliant lecturer who improvised, rapidly and spontaneously, richly allusive and coherently structured material. He translated works by Turgenev from Russian into English and, during the war, worked for the British Diplomatic Service. The Independent stated that "Isaiah Berlin was often described, especially in his old age, by means of superlatives: the world's greatest talker, the century's most inspired reader, one of the finest minds of our time... there is no doubt that he showed in more than one direction the unexpectedly large possibilities open to us at the top end of the range of human potential".

In 1932, at the age of 23, he was elected to a prize fellowship at All Souls College, Oxford. From 1957 to 1967, he was Chichele Professor of Social and Political Theory at the University of Oxford. He was president of the Aristotelian Society from 1963 to 1964. In 1966, he helped to found Wolfson College, Oxford, and became its first President. He was knighted in 1957, and was awarded the Order of Merit in 1971. He was President of the British Academy from 1974 to 1978. He also received the 1979 Jerusalem Prize for his writings on individual freedom. The annual Isaiah Berlin Lectures are held at both Oxford and the British Academy each summer. Berlin's work on liberal theory has had a lasting influence.