Prince Harry and Meghan Markle have been declared husband and wife after exchanging vows and rings in front of 600 guests, including the Queen.
In departures from British royal custom, Harry will wear a ring, while Markle did not vow to obey her husband.
Ms Markle, who will now become the Duchess of Sussex, wore an elegant white silk dress by Clare Waight Keller for the House of Givenchy.
She arrived at St George's Chapel to a fanfare and walked down the aisle accompanied part of the way by Prince Charles, and by 10 young page boys and bridesmaids.
The children include 4-year-old Prince George and 3-year-old Princess Charlotte, children of Prince William and the Duchess of Cambridge.
As they stood at the altar, Harry said to his bride: "You look amazing."
Ms Markle's mother, Doria Ragland, sat opposite alone the royal family.
The Queen was accompanied by her husband Prince Philip, 96, who underwent hip surgery earlier this year.
Celebrities, sportsmen, military, aristocracy and family arrived earlier at St George's Chapel at Windsor Castle for the royal wedding.
Oprah Winfrey, George and Amal Clooney, Elton John, Victoria and David Beckham and Serena Williams were among the star names.
The Duchess of Cambridge's family, Carole and Michael Middleton, James and Pippa, Harry's cousin Zara and her husband Mike Tindall, and Spencer family members, including Diana's brother, Earl Spencer.
Diana's sister Lady Jane Fellowes gave the reading.
Earlier, Queen Elizabeth bestowed the title of Duke of Sussex on her grandson, a step that means the American actress, star of the TV drama Suits, will become a duchess when she marries Harry.
Under clear skies and glorious sunshine, a military band in scarlet uniforms and bearskin hats entertained thousands of excited fans gathered behind barriers.
Police armed with semi-automatic rifles patrolling streets and watching from rooftops.
The couple, who met on a blind date in 2016 and fell in love in a tent under the stars in Botswana, will tie the knot at the 15th-century St George's Chapel, in a castle that has been home to 39 English monarchs since 1066.
More than 100,000 fans are expected to cram the narrow roads of Windsor, about 30 km west of London. Visitors had to pass through police search points set up around the castle.
Hundreds of TV crews from around the world have descended on Windsor for the union of Harry, 33, sixth-in-line to the British throne, and Markle, 36, a divorcee whose mother is African-American and father is white.
The service was conducted by the Dean of Windsor with Justin Welby, Archbishop of Canterbury and spiritual head of the Anglican Church, overseeing the exchange of vows.
- Meghan feels 'wonderful' ahead of wedding
- Famous faces to spot at the royal wedding
- Sydney koalas named after Harry and Meghan
- Prince Harry and Meghan Markle's romance
- The Royal Wedding 2018 tea drinking game
A black US bishop, Michael Bruce Curry, gave the wedding address.
In among traditional hymns, a choir performed American soul singer Ben E. King's 1960s hit Stand By Me.
After the ceremony, the newlyweds are expected to greet some of the 1200 members of the public invited into the castle grounds before starting a carriage procession through Windsor.
A reception will be held in the castle's St George's Hall before 200 guests join the couple at an evening event at the nearby Frogmore House mansion.
The newlyweds are not immediately leaving on honeymoon and will carry out their first official engagement as husband and wife next week.
Australian Associated Press