Peter Bernard Clarke (25 October 1940 – June 2011) was a British scholar of religion and founding editor of the Journal of Contemporary Religion.
Clarke served as Professor Emeritus of the History and Sociology of Religion at King's College London, having taught there from 1994 to 2003, the Director of the Centre for New Religions at King's College, and a professorial member of the Faculty of Theology at the University of Oxford (since 2003); earlier in his career (1974–1978) he was Professor of African History at the University of Ibadan, Nigeria.
Clarke inaugurated a series of annual conferences on new religious movements at King's, which brought together academics from a variety of backgrounds. These conferences eventually evolved into the "INFORM" (Information Network Focus on Religious Movements) seminars.
Clarke was the founding editor of the Journal of Contemporary Religion, established by the Centre for New Religions in 1985 (the journal appeared under the title Religion Today until 1995).
Clarke's research fields have spanned Islamic movements as well as new religions derived from African, African Brazilian and Japanese roots. His publications include Religion Defined and Explained 1993, with Peter Byrne), Japanese New Religions: In Global Perspective (2006, editor), New Religions in Global Perspective: A Study of Religious Change in the Modern World, the Encyclopedia of New Religious Movements (2005, editor), and The Oxford Handbook of the Sociology of Religion (2008, editor); he is also the author and editor of another 20 books and 100 scholarly articles.
In Religion Defined and Explained, co-written with Peter Byrne, Clarke advocated an elastic definition of religion based on "family resemblance": while religions have "a characteristic set of features", "there will be no single feature or set of features found in each and every example of religion", and "there will be no limits to be set in advance to the kind of characteristic features newly discovered or developing religions might be found to exemplify, nor will there be absolute limits to the additional features such new examples could add to the set". Clarke and Byrne argued that "the various examples of religion will then be related by a network of relationships rather than shared possession of necessary and sufficient conditions for membership of the class." Even so, based on the family resemblance, "one will be able to say of newly found examples whether they are religions or not."