Dr Williams, a Welshman, is a formidable theologian
World poverty has long been an issue highlighted by the Archbishop of Canterbury.
The head of the Church of England used his Christmas sermon to warn that a secure world would only be possible if the rich shared their wealth, justice and liberty with poorer nations.
He accused some countries of concentrating on terrorism and failing to reach their own development goals. He also stressed the importance of halving world poverty by 2015 - a goal which he said had not moved on for four years.
Dr Rowan Williams urged Christians to engage the world of politics after being enthroned as the 104th Archbishop of Canterbury in February 2003.
"When Christians grieve or protest about war, about debt and poverty, about prejudice, about the humiliations of unemployment... it is because of the fear we rightly feel," he said.
Dr Williams has become known as an opinionated archbishop, quick to share his moral, religious and political views.
He has also presided over a turbulent time for the church and a testing time for the UK since his appointment.
Dr Williams has made his views against the war in Iraq clear.
He has praised the men and women serving in the Gulf for their courage and dedication. But said the aftermath of the Iraq war has resulted in a loss of trust in the nation's political system.
The archbishop has also courted controversy with his objection to anti-gay views in the church and his support for the ordination of women priests.
Earlier this year, the archbishop called on Anglican leaders to put their differences over the issue of gay clergy aside for the sake of the Church.
The archbishop is a high-profile figure and appeared on the world stage recently following the appointment of a new Pope.
Dr Williams greeted the new Pope in German
He gave Pope Benedict XVI a pectoral cross as a present when he led Anglican representatives in the Vatican in a meeting with the pontiff.
Weeks earlier, Dr Williams played an important role on the national stage - conducting the blessing of prayer and dedication following the wedding of Prince Charles and Camilla.
The lot of an Archbishop of Canterbury has never been an easy one.
Some, like Thomas a Becket, have been murdered. Others, most notably Thomas Cranmer, have met their end courtesy of the executioner.
Archbishops have been used as political pawns by monarchs, ridiculed as meddlesome priests by politicians and scoffed at as wishy-washy liberals by the media.
But the 104th Archbishop in the post faces contemporary crises.
A formidable theologian with an outstanding track record, Dr Williams, who published his first book at the age of 29, was only 36 when he was appointed professor of divinity at Oxford - the university's youngest professor.
The blessing of the royal wedding at St George's Chapel was televised
He is the first Welshman - indeed he is a fluent Welsh speaker - to serve as Archbishop of Canterbury for at least a millennium.
Dr Williams' major problem rests with his unique position.
As Archbishop of Canterbury he is leader of the 77 million-strong worldwide Anglican Communion but, unlike the Pope, he has no power to force any of his 38 archbishops to submit to his will.
The broad nature of the Church, which includes anglo-Catholics, evangelicals and liberals, means that it is almost impossible for it to achieve unity on many controversial matters, including the ordination of women, human sexuality and relations with Rome.
But he has proved he can engage with public debate - praising Philip Pullman's His Dark Materials works, despite them being interpreted by some as anti-Christian.
He then took part in a high-profile debate with the author.
In the church itself, whatever the divisions, he has also impressed with his intellect, common sense and charisma.