WINDSOR, England — America has a new princess.

Los Angeles native Meghan Markle joined hands with Britain’s Prince Harry Saturday as they pledged to “honor and protect” each other in marriage after a 15-month romance. They later shared a kiss on the steps outside the chapel.

Wearing a tiara and a flowing white dress, the former "Suits" star began her latest role at a ceremony that brought modern soul to the traditional pomp and pageantry of a royal wedding.

As the couple stood inside St. George’s Chapel at Windsor Castle, a gospel choir sang Ben E. King’s “Stand by Me.”

With their vows, the couple adopted their new official title, the Duke and Duchess of Sussex.

The historic moment was witnessed by 600 guests — including Oprah Winfrey, George and Amal Clooney and Elton John — a flag-waving crowd of around 100,000 outside, and millions of TV viewers around the world.

The crowd cheered wildly as the bride began her long walk down the aisle in a dress designed by Clare Waight Keller, who last year became the first female artistic director at the French fashion house Givenchy.

As she reached the altar, Harry bit his lip and told her: "You look amazing."

The Most Rev. Michael Bruce Curry, the presiding bishop of the Episcopal Church who hails from Chicago, gave a lively address quoting Martin Luther King Jr. on the "redemptive power of love."

Turning to the couple, he joked: “We gotta get y’all married.”

A few feet away were two women: Doria Ragland, the bride’s mother who works as a yoga instructor and social worker in California, and Queen Elizabeth II, the longest-serving British monarch. The actress' father, Thomas Markle, was too sick to attend.

The scenes would have been unthinkable in royal circles until recently. The last time an American married a British royal was in 1936. Wallis Simpson’s status as divorcee caused a scandal that led King Edward VIII to abdicate.

The new princess is not only a divorcee but, in her own words, a "strong, confident mixed-race woman.” While hardly a revolution in 2018, her arrival brings diversity to her new extended family and she has been warmly embraced by the British public. In a break with tradition, she often hugs people she meets.

The couple also invited 2,640 members of the public to the castle's grounds, including local children and community leaders.

"They want to share their happiness with the public," said Roya Nikkhah, royal correspondent for The Sunday Times. The couple “want to be seen as open, not elitist, modern,” she said.

The American royal, who visited Buckingham Palace as tourist while a teenager, sang along to “God Save the Queen” as the ceremony drew to a close.

The 15th-century St. George’s Chapel, whose vaulted ceilings and stained-glass windows make it one of the finest examples of Gothic architecture in England, echoed with the song “This Little Light of Mine” by Etta James as the newlyweds departed, pausing on the steps for a kiss.

The royal newlyweds then took a trip through Windsor in a horse-drawn carriage, to the delight of thousands of well-wishers who gathered in the late spring sunshine.

Harry, who served in the army for 10 years and rose to the rank of captain while completing two tours in Afghanistan, wore the ceremonial uniform of the Blues and Royals army regiment.

Markle did not have a maid of honor because, as the palace explained, she couldn't choose between her close friends. However, the couple have chosen 10 bridesmaids and pageboys, including Harry's nephew, Prince George, and niece, Princess Charlotte.

In a nod to Markle’s American roots, the couple's cake was made by an American baker based in London, Claire Ptak, who had previously appeared on Markle’s lifestyle blog, The Tig. The ink used on the formal invitations was also from the U.S.

Since their engagement, the couple has toured the U.K., visiting cities in England, Scotland, Wales and Northern Ireland.

Meghan Markle and Prince Harry leave St. George's Chapel at Windsor Castle after their wedding. Gareth Fuller / Reuters

Markle has been welcomed into royal circles, accompanying Harry to family functions including Christmas with the queen at her country retreat in Sandringham, Norfolk, and the Commonwealth Day ceremony at Westminster Abbey where she sat in the row behind the queen.

In the future, they are expected to continue Harry’s charity work, much of which is done jointly with his brother, Prince William, and William's wife, the former Kate Middleton, including their Heads Together campaign promoting mental health. The two couples have been affectionately dubbed the "fab four" by Britain's media.

Markle becomes a princess automatically by marrying Harry. As she was not born a royal, her title as princess becomes her husband's name, so she'll formally be known as Her Royal Highness Princess Henry of Wales.

Rachel Elbaum and Alastair Jamieson reported from London, and F. Brinley Bruton and Petra Cahill reported from Windsor, England.