Dewi Zephaniah Phillips (24 November 1934 – 25 July 2006), usually cited as D. Z. Phillips, was a Welsh philosopher and theologian. Phillips was a leading proponent of the Wittgensteinian philosophy of religion.

Phillips was born in Morriston, Swansea, into a Congregational family on 24 November 1934. He was the youngest of the three sons of David and Alice Phillips. He attended the former Swansea Grammar School. Phillips studied philosophy at Swansea University from 1952 to 1958, where his teachers included J. R. Jones, R. F. Holland, Peter Winch, and, most importantly, Rush Rhees. From 1958 to 1961, he then studied at the University of Oxford, where he matriculated at St Catherine's College. While he was at Oxford he undertook a dissertation which Anglican philosopher Michael Foster initially tutored and which Rush Rhees later supervised. In 1965 his dissertation became the source for his first book The Concept of Prayer.

After his graduation from the University of Oxford, Phillips began his academic career in 1961 as an assistant lecturer in philosophy at Queen's College, Dundee. In the following year he became a lecturer. In 1963 he obtained a post as lecturer in philosophy at the University College of North Wales, Bangor.

In 1965 Phillips returned to Swansea University, to take up a lectureship in the Department of Philosophy. He was promoted to a senior lectureship in 1967. In 1971 he became its professor and head of department. He was also Dean of the Faculty of Arts (1982–1985) and Vice-Principal (1989–1992). His research interests included the philosophy of religion, ethics, philosophy and literature, Simone Weil, Søren Kierkegaard, and Ludwig Wittgenstein.

In 1992 Phillips was appointed Danforth Professor of Philosophy of Religion at the Claremont Graduate University in California, and thereafter divided his time between Claremont and Swansea where, in 1996, he became the Rush Rhees Professor Emeritus and Director of the Rush Rhees Archives and Peter Winch Archives based in Swansea University.

While at Swansea, Phillips made a substantial contribution to the University's reputation as a centre of Wittgenstein's philosophy, the Swansea School of Philosophy. Scottish Dominican Fergus Kerr noted: 'He became the best known of the "Swansea Wittgensteinians": philosophy understood as a kind of intellectual therapy in dark times rather than constructive theorizing; against prevalent aspirations and practice in the discipline, philosophical work as reminding ourselves of things we may overlook but cannot deny, rather than adding to the sum of knowledge by quasi-scientific discoveries.'

The Swansea school of thought is, perhaps, most thoroughly articulated as a positive research program in Phillips' own book on the subject, "Philosophy's Cool Place" (1999), in which he argues for the merits of "contemplative philosophy". On this view, philosophy is an activity involving both inquiries about reality and elucidations of the various contexts in which people live and speak. In contrast to the New Wittgenstein school of thought, philosophy is not limited to purely "therapeutic" treatments and the removing of philosophical confusion. Here, Phillips is primarily indebted to the work of Rush Rhees. For Phillips, what gives philosophy its unique disciplinary feature is its primary concern with the question of the nature of reality: "How can philosophy give an account of reality which shows that it is necessary to go beyond simply noting differences between various modes of discourse, without invoking a common measure of 'the real' or assuming that all modes of discourse have a common subject, namely, Reality?".

Phillips gave many endowed lectures during his tenure at California's Claremont Graduate University. These included the Cardinal Mercier Lectures (Leuven), Marett Lecture (Oxford), Riddell Lectures (Newcastle), McMartin Lectures (Carleton University, in Ottawa), Hintz Lecture (Tucson), the Aquinas Lecture (Oxford), and Vonhoff Lectures (Groningen).