Peter Phillips, the Queen's eldest grandson, has married his Canadian bride Autumn Kelly in Windsor Castle's St George's Chapel.
The couple were joined by 300 guests, including most of the Royal Family.
They exchanged vows in an hour-long ceremony, before heading to a reception and dance at Frogmore House in Windsor in a horse-drawn carriage.
Cheers and clapping were heard outside the chapel as the couple, who are both aged 30, walked down the aisle.
The groom is the only son of Princess Anne and her first husband, Captain Mark Phillips and is 11th in line to the throne.
His bride, a management consultant, wore a dress by London designer Sassi Holford with a full veil, a tiara on loan from her mother-in-law Princess Anne, and a necklace and earrings from Mr Phillips.
She was attended by six bridesmaids, including Peter's sister Zara Phillips, in sage green dresses by Vera Wang.
Showers dampened her arrival, but had subsided by the time she left the chapel as Mrs Autumn Phillips.
Her husband does not have a royal title because Princess Anne turned down the Queen's offer of honours for both her children.
The service was led by the Right Rev David Conner, Dean of Windsor.
Among those watching the couple exchange vows were the Queen, Duke of Edinburgh, Prince of Wales and Duchess of Cornwall.
Prince Harry, his girlfriend Chelsy Davy, and Prince William's girlfriend Kate Middleton were also present.
Prince William was unable to attend because he is in Kenya at the wedding of a friend.
Princess Eugenie read Shakespeare's sonnet 116 and Patrick Kelly, the bride's half-brother, read from Chapter 3 of St Paul's letter to the Colossians.
About 70 of the 300 guests flew over from Canada for the occasion.
The couple met in 2003 at the Montreal Grand Prix where they were both working. Mr Phillips proposed last July.
The new Mrs Phillips gave up her Catholic faith and converted to the Church of England, enabling Mr Phillips to retain his right to the throne.
Since 1701, heirs to the throne marrying Catholics cannot become sovereigns.
They have not revealed where they are going on honeymoon, other than it is somewhere hot.
BBC royal correspondent Daniela Relph said the couple had sold the story of their relationship to Hello! magazine - a decision which has raised a few eyebrows in royal circles.
It has been reported they were paid £500,000.
Royal commentator Richard Fitzwilliam told BBC News the wedding was representative of a new trend in royal marriages.
"Royals aren't marrying other royals and aren't marrying into the upper classes," he said. "They're marrying into the middle class and they're marrying for love.
"Which of course is how it should be and it has this sort of reviving effect - new ideas, new trends - and it means that royal houses won't be so alone. They won't be so fossilised "