Isaiah Berlin (Riga, 1909-Oxford, 1997), British historian of ideas and political philosopher of Russian-Jewish origin, is one of the most prominent liberal thinkers of the 20th century, who acquired relevance for his two concepts of freedom (negative and positive) and by his notion of the pluralism of values.

Born in Livonia, then part of the Russian Empire, he moved with his family to Saint Petersburg at the age of six. After witnessing the Bolshevik Revolution, the family emigrated in 1921 to the United Kingdom, where Berlin obtained a scholarship at All Souls College, Oxford, a University to which he would be linked throughout his academic life, since there he was a professor of Social and Political Theory between 1957 and 1967 and helped found Wolfson College, of which he was its first president.

Among his works (for the most part, compilations of texts from various sources edited or co-edited by Henry Hardy) include Karl Marx (1939), The Hedgehog and the Fox (1953), Two Concepts of Freedom (1958), Four Essays on the freedom (1969), Vico and Herder (1976), Russian thinkers (1978), Concepts and categories (1978), Against the current (1979), The crooked shaft of humanity (1990), The magician of the north (1993), The sense of reality (1996), The roots of Romanticism (1999) and The power of ideas (2000).