Rowan Douglas Williams, Baron Williams of Oystermouth (born 14 June 1950), is a Welsh Anglican bishop, theologian and poet, who served as the 104th Archbishop of Canterbury from 2002 to 2012. Previously the Bishop of Monmouth and Archbishop of Wales, Williams was the first Archbishop of Canterbury in modern times not to be appointed from within the Church of England.

Williams's primacy was marked by speculation that the Anglican Communion (in which the Archbishop of Canterbury is the leading figure) was fragmenting over disagreements on contemporary issues such as homosexuality and the ordination of women. Williams worked to keep all sides in dialogue. Notable events during his time as Archbishop of Canterbury include the rejection by a majority of dioceses of his proposed Anglican Covenant and, in the final general synod of his tenure, his unsuccessful attempt to secure a sufficient majority for a measure to allow the appointment of women as bishops in the Church of England.

Having spent much of his earlier career as an academic at the universities of Cambridge and Oxford successively, Williams speaks three languages and reads at least nine.

Williams retired as Archbishop of Canterbury on 31 December 2012 and was succeeded by Justin Welby. On 26 December 2012, 10 Downing Street had announced Williams's elevation to the peerage as a life peer, so that he could continue to speak in the House of Lords. Following the creation of his title on 8 January and its gazetting on 11 January 2013, he was introduced to the temporal benches of the House of Lords as Baron Williams of Oystermouth on 15 January 2013, sitting as a crossbencher. Oystermouth is a district of Swansea.

Williams delivered the Gifford Lectures at the University of Edinburgh in 2013 and served as Master of Magdalene College, Cambridge, between 2013 and 2020. He took up the position of chancellor of the University of South Wales in 2014. He retired from the House of Lords on 31 August 2020 and from Magdalene College that autumn, returning to Abergavenny in his former Diocese of Monmouth.

Williams was born on 14 June 1950 in Swansea, Wales, into a Welsh-speaking family. He was the only child of Nancy Delphine (known as "Del") (née Morris) and Aneurin Williams  – Presbyterians who became Anglicans in 1961. He was educated at the state sector Dynevor School, Swansea, before reading theology at Christ's College, Cambridge, where he graduated with starred first-class honours. He then went to Wadham College, Oxford, where he studied under A. M. Allchin and graduated with a Doctor of Philosophy degree in 1975 with a thesis entitled "The Theology of Vladimir Nikolaievich Lossky: An Exposition and Critique".

Williams lectured and trained for ordination at the College of the Resurrection in Mirfield, West Yorkshire, for two years (1975–1977). In 1977, he returned to Cambridge to teach theology as a tutor (as well as chaplain and director of studies) at Westcott House; he was made a deacon in the chapel by Eric Wall, Bishop of Huntingdon, at Michaelmas (2 October). While there, he was ordained a priest the Petertide following (2 July 1978), by Peter Walker, Bishop of Ely, at Ely Cathedral.

On 4 July 1981, Williams married Jane Paul, a writer and lecturer in theology. They have two children.