Police estimate a million people lined the procession route from the abbey to the palace.
The bride will now be Her Royal Highness the Duchess of Cambridge.
Prince William drove his new bride back to Clarence House, following a buffet reception at Buckingham Palace, in Prince Charles's classic blue Aston Martin, decked in ribbons and balloons with "Just Wed" on the number plate.
They will return to the palace for evening celebrations later.
The church service, watched by 1,900 guests, 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.
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.
The duchess, who managed to keep her wedding dress a secret, wore an ivory and lace gown by Sarah Burton at Alexander McQueen. The prince wore the red tunic of an Irish Guards colonel - his most senior honorary appointment.
At the sceneThe excitement, which had been building throughout the morning, peaked at about 1330 BST when the prince kissed his new bride.
The crowd, decked in union jacks, tiaras, and fascinators, reacted with deafening cheers and demands for more.
Much neck-craning was required for the best view of the spectacle, which was obscured by a sea of cameras, periscopes and flags.
Some people had tears in their eyes as they watched the fly-past, with "amazing" a common response when asked about the day's events.
As one American spectator put it, "No-one does pageantry like the British - you can't help being infected by the energy and emotion."
Continue reading the main story
UK Prime Minister David Cameron and his wife Samantha, Australian prime minister Julia Gillard and former British PM Sir John Major were among the politicians present.
For those lining the route, large speakers broadcast the wedding service, and hundreds of millions of people were estimated to watch the proceedings worldwide on television.
- According to a lip-reading expert, Prince William told his bride she looked "beautiful" as she joined him at the altar and joked to his father-in-law Michael: "We're supposed to have just a small family affair"
- The fly-past at Buckingham Palace involved Lancaster, Spitfire and Hurricane aircraft from the RAF's Battle of Britain Memorial Flight
- 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, military personnel and representatives of various faiths and charities
- After the service, the newly-weds travelled in an open-topped carriage for the 15-minute journey from Westminster Abbey to Buckingham Palace, past London landmarks, including the Houses of Parliament, Big Ben and Horse Guards Parade
- More than 1,000 military personnel and musicians lined the procession route
- Thousands of street parties were held around the UK, and big screens were put up in many towns and cities. The BBC has been bringing viewers and listeners comprehensive coverage across TV, radio and online, in the UK and around the world
- 5,000 police officers were on duty, with more than 900 along the wedding route
- Police have made 57 arrests in and outside the security zone and questioned masked protesters in central London.
- About two square miles of central London were closed to traffic.
- A yellow RAF Sea King rescue helicopter flew over The Mall as the couple drove to Clarence House. It was a surprise for the groom, a search and rescue helicopter pilot.
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.
But the Queen and the Duke of Edinburgh left 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.
Despite predictions of showers, it stayed dry for the royal couple. Temperatures in London reached around 18C (64.4F) at 2pm.