The Most Rev Justin Welby has arrived at Canterbury Cathedral for his enthronement.
Prime Minister David Cameron, the Prince of Wales and the Duchess of Cornwall are among those watching as the Most Rev Welby becomes the Archbishop of Canterbury.
The Archbishop of York has offered a prayer for the Most Rev Justin Welby before his enthronement today.
Dr John Sentamu said: "As we welcome the inauguration of our brother Justin as Archbishop of Canterbury, let us all join together in saying this prayer today:
"May God, who anointed the Christ with the Holy Spirit at His baptism, anoint and empower Archbishop Justin to bring good news to the poor, to proclaim release to the captives, to set free those who are oppressed and to proclaim the acceptable year of the Lord.
"May the Lord keep him in the joy, simplicity and compassion of His Holy Gospel."
Religious leaders from across the globe are set to join royalty and senior politicians for the enthronement of the Archbishop of Canterbury.
The Most Rev Justin Welby will formally begin his public ministry as head of the Church of England, spiritual leader of the 77-million strong Anglican Communion and 105th Archbishop of Canterbury at a service in Canterbury Cathedral.
The Prince of Wales and the Duchess of Cornwall as well as Prime Minister David Cameron will be among around 2,000 people attending the ceremony.
Those also in the congregation will include representatives of major world religions including Muslims, Jews and Sikhs and senior figures from the Roman Catholic and orthodox churches.
The event marks the formal reception of the Most Rev Welby, 57, at Canterbury, the mother church of the Church of England and of the Anglican Communion.
The Most Rev Justin Welby said he believes a woman will one day be made archbishop and added that some gay couples have loving relationships of "stunning quality", ahead of today's enthronement.
Pressed on the timing, he said: "Oh, I have no idea...when the right person turns up. But, yes, I think there certainly will."
In a separate interview with BBC News, the Most Rev Welby backed traditional Church teaching on homosexuality but said: "You see gay relationships that are just stunning in the quality of the relationship."
The Most Rev Justin Welby has given his "profound thanks" to everyone preparing for his enthronement as the Archbishop of Canterbury.
Out early this morning, Canterbury is beautiful, human scale and history falling out of the walls everywhere. Grateful to be here.
Everywhere signs of preparation for the service today on Canterbury. So many people working so hard, profound thanks to them all, incl media
He has spoken to ITV News Social Affairs Editor Penny Marshall about his fears for the day and said he would mainly be wondering, "where am I meant to go next, and I hope I don't go the wrong way" during the elaborate ceremony: