Williams, 52, currently the archbishop of Wales, officially takes over from incumbent of 11 years George Carey in October as spiritual leader of the world's Anglicans.
He becomes the first Welshman selected for the post for at least 1,000 years.
Williams, who aged 36 became Oxford university's youngest professor of divinity, is also sympathetic to the proposal that the Church of England should lose its established status as England's official church, another view that does not endear him to traditionalists.
Conservative Christians have already warned that they are uncomfortable with his support for the ordination of women and homosexual priests.
A married father of two, Williams is not afraid to speak his mind.
He has attacked the US-led military campaign in Afghanistan after September 11 as "morally tainted," and last week signed a letter condemning an attack on Iraq as "immoral and illegal."
On the eve of his appointment, Williams has had his new book serialized in The Times, in which he attacks the corruption and premature sexualization of young children by the consumer society.
He criticizes the way consumerism intrudes into children's lives through "tie-ins" of candy and toys with films and television programs, singling out the Disney Corporation.
In another stance likely to arouse controversy, recent reports have suggested that Williams will give his blessing to heir to the throne Prince Charles marrying his long-time companion Camilla Parker Bowles in church.
Although Charles has been technically free to remarry in church, the fact his mother Queen Elizabeth is the supreme governor of the Church of England -- a role he will assume on his ascension to the throne -- has effectively barred him from such a step.
Williams, a philosopher, poet, and linguist who speaks seven languages, will lead 70 million Anglicans worldwide in his post as archbishop of Canterbury.
He also has a sense of humour. He has dubbed the American cartoon "The Simpsons," of which he is a huge fan, as "one of the most subtle pieces of propaganda around in the cause of sense, humility and virtue."
Williams studied theology at the prestigious Cambridge University, where he met his wife Jane, also a theologian. The couple have two children, Rhiannon, 14, and Pip, six.
Williams has written on a broad range of topics including the Resurrection, the theology of nuclear deterrence, early church heresy, and Russian Orthodoxy.
He became involved in the Campaign for Nuclear Disarmament and was arrested in 1985 for singing psalms on a US airbase in Cambridgeshire, southeast England.
His academic career took him to the prestigious Oxford University, where his fellow dons were reportedly surprised when, after just six years, he left to become Bishop of Monmouth, southeast Wales, in 1992.
He proved highly popular in Wales and in 2000, fellow bishops in the Welsh Anglican church elected him their archbishop.
Some aspects of his make-up are surprisingly conservative. He is said to be morally uncomfortable with abortion. He enjoys the language of the traditional edition of the Bible, the King James version.
He is also a lover of Baroque music.