Prince William and Kate Middleton have been pronounced man and wife at Westminster Abbey.
Some 1,900 guests watched the couple exchange their vows, with many millions watching at home.
They left the Abbey, with Kate Middleton now the Duchess of Cambridge, amid cheers from thousands of well-wishers lining the procession route.
They are now at Buckingham Palace where the Queen is hosting a buffet reception for 650 guests.
The couple travelled in an open-topped 1902 State Landau carriage for the procession, which was used by Prince William's parents for their wedding in 1981.
The couple are due to appear on the balcony at about 1325 BST.
Prince William has been given the title of the Duke of Cambridge by the Queen, and Miss Middleton has become Her Royal Highness the Duchess of Cambridge.
The church service ran smoothly but the prince did struggle to place the wedding ring on the duchess's finger.
Following a long tradition, the ring has been fashioned from Welsh gold given to Prince William by the Queen.
After the couple said their vows, in which she did not promise to obey William, the Archbishop of Canterbury, the Most Reverend Rowan Williams, declared: "I pronounce that they be man and wife together, in the name of the Father, and of the Son, and of the Holy Ghost. Amen."
They spent a private moment together with their families, as they signed the marriage register.
The duchess, who managed to keep her wedding dress a secret, is wearing an ivory and lace gown by Sarah Burton at Alexander McQueen. The prince is wearing the red tunic of an Irish Guards colonel - his most senior honorary appointment.
Prince William has been given the title of the Duke of Cambridge by the Queen, and Miss Middleton has become Her Royal Highness the Duchess of Cambridge on their marriage.
Well-known faces spotted at Westminster Abbey included singer-songwriter Sir Elton John and his partner David Furnish, former England rugby coach Sir Clive Woodward, and former England football captain David Beckham and his wife Victoria.
Actor Rowan Atkinson, a close friend of Prince Charles, Prince Harry's friend Chelsy Davy and film director Guy Ritchie were also there.
UK Prime Minister David Cameron and his wife Samantha, Australian prime minister Julia Gillard, former British PM Sir John Major, and current Home Secretary Theresa May were among the politicians present. Mr Cameron did not cause an etiquette upset and wore a morning suit despite initially suggesting he might not.
For those lining the route, large speakers broadcast the wedding service, and it was anticipated the event would be watched by hundreds of millions of people worldwide on television.
- The busy schedule began when guests start arriving at the Abbey from 0815 BST. Many had been queuing before the Great North Door opened
- A Rolls-Royce picked up Miss Middleton at the Goring Hotel, where the Middleton family were staying, at 1050BST. Prince William travelled to the Abbey with his brother and best man in a Bentley
- Out of the 1,900 guests at the Abbey, 1,000 were friends and family, who had been given some of the best seats in the house. The others included overseas royals, politicians from home and abroad, military personnel and representatives from various faiths and charities
- After the service, the newlyweds travelled in an open-topped carriage for the 15-minute journey from Westminster Abbey to Buckingham Palace, past some of London's most famous landmarks, including the Houses of Parliament, Big Ben and Horse Guards Parade.
- Thousands of street parties are being held around the UK, and big screens have been put up in many towns and cities. The BBC will be bringing viewers and listeners comprehensive coverage across TV, radio and online, both in the UK and around the world
- 5,000 officers are on duty, with more than 900 along the wedding route. Most are in uniform, but some will be in plain clothes, mixing with the crowd
- About two square miles of central London have been closed to traffic.
Royal officials said William and Kate were involved in planning their wedding day, from the music at the ceremony to the flowers and the cake.
Inside Westminster Abbey, an avenue of trees lined the red carpet leading up to the altar.
The bride walked up the aisle to coronation anthem I Was Glad, by Sir Charles Hubert Hastings Parry, from Psalm 122. Her brother James Middleton gave the Lesson, reading Romans 12: 1-2, 9-18.
Classical compositions by Elgar, Britten and Vaughan Williams featured during the ceremony, alongside the hymn Jerusalem and the English melody Greensleeves.
About 300 close friends and relatives will stay on at Buckingham Palace for a formal black tie dinner and disco in the evening.
But the Queen and the Duke of Edinburgh will leave for a weekend away after hosting the lunchtime reception and will miss Prince Harry's best man speech and Michael Middleton's father of the bride address.
Prince William's choice of a military uniform for his wedding was something of a surprise, royal watchers say. As a search and rescue helicopter pilot in the Royal Air Force, many had predicted he would wear his blue flight lieutenant's uniform.
However, as an honorary colonel of the Irish Guards infantry regiment, he opted to wear the red tunic and forage cap.
Prince Harry is a captain in the Household Cavalry's Blues and Royals regiment and is wearing his uniform, while Prince Charles is in his Royal Navy admiral's outfit.
The day has been dry and cloudy in London but the Met Office says there is a risk of heavy showers developing later on. Temperatures in the capital are expected to reach a high of 19C (66F) in the afternoon.