LONDON — Prince Harry could barely contain himself. Facing a news camera to announce his son’s birth, he rubbed his hands together, bounced on the balls of his feet and seemed unable to stop himself from grinning, even for a second.

“It’s been the most amazing experience I can ever possibly imagine,” he said, standing in front of the stables at Windsor Castle, where two black horses nodded behind him.

“How any woman does what they do is beyond comprehension, and we’re both absolutely thrilled,” he said about his wife, Meghan, the Duchess of Sussex. The duchess, he said, was “amazing,” and the birth “amazing,” and the love and support from the public “amazing.” Then he turned to go, so addled with happiness and sleep deprivation that he appeared to thank the horses.

“This little thing is absolutely to die for, so I’m just over the moon,” he managed.

If much of the world was drawn into the child’s birth, a few minutes after dawn on Monday, it was not purely because of the newborn’s position, seventh in line to the British throne.

It was also because he represents change for the oldest of houses. He is half American, descended on his mother’s side from a bellhop in a Cleveland hotel, a laundry worker in Chattanooga, and a bartender in an Atlanta saloon. And he is the first multiracial baby in the British monarchy’s recent history, an instant star in a country where multiracial children make up the fastest-growing ethnic category.

We have been waiting for him,” said Carol Lengolo, 38, who moved to Britain from South Africa and is raising a son and a daughter in southeast London. She said that she had set up multiple notifications so the family would know the moment the child was born and that when word came through, at 2:39 p.m., they began screaming and ran to the television.

“We feel like Meghan is one of us, so we are supporting her,” she said. “We can’t wait to see what he looks like.”

It is not clear whether the newborn, who falls behind Harry in the line of succession, will receive a royal title, like those bestowed on the three children of Prince William, Harry’s older brother, and William’s wife, Catherine.

Buckingham Palace said that Meghan gave birth at 5:26 a.m. and that her mother, Doria Ragland, was with the new parents at their home, Frogmore Cottage. The newborn boy weighed 7 pounds, 3 ounces, the royal couple wrote on Instagram; a name had not been chosen yet.

The duchess was reported to be hoping for a home birth, but she had passed her due date, and late on Monday, some British news outlets were reporting that she was whisked away on Sunday for a hospital delivery.

Prince Harry, in his comments on Monday, said the family would meet with members of the news media in two days, “as a family, to be able to share it with you guys, and so everyone can see the baby.”The baby is sure to be the object of uncommon fascination, adored and criticized as a symbol of the modernization of Britain’s royal family.

Harry, 34, and Meghan, 37, have shaken up the royal family in a number of ways: The duchess is an American and a former actress, and their wedding last May featured a gospel choir, a freestyling African-American bishop and a gaggle of Hollywood celebrities.

They continued to set aside convention after the wedding, opening their own Instagram account and offering little access to the royal-obsessed British news media. In April, they announced they were canceling the traditional photo opportunity outside the Lindo Wing at St. Mary’s Hospital in the heart of London, curtailing the ritual hullabaloo that usually surrounds royal births.

For many, the new baby’s importance will be indelibly linked with race.

Britain is 87 percent white, but multiracial people will soon be the country’s largest minority group. The entry of Meghan Markle, the descendant of plantation slaves, into the royal family resonated deeply with many people of African descent, who almost immediately began to anticipate the birth of the couple’s first child.

prince Harry, in particular, has been alert for racism in the discussion of his young family.

In 2016, he took the unusual step of condemning British tabloids and social media commentators for the “racial undertones” and sexism of their coverage of Ms. Markle. Last year, the right-wing U.K. Independence Party ousted its leader after it was reported that his girlfriend had used racist language to deride the future duchess.

Meghan, the daughter of a white man and a black woman, grew up in a mostly white neighborhood, where her mother was sometimes mistaken for her nanny. In an essay, she described hesitating, as a schoolgirl, when she was asked to fill out a census form that identified her as either white or black.

There I was (my curly hair, my freckled face, my pale skin, my mixed race) looking down at these boxes, not wanting to mess up, but not knowing what to do,” she wrote in an essay for Elle magazine published in 2015.

When her teacher told her to check “Caucasian” because that was “how she looked,” she refused.

“I left my identity blank — a question mark, an absolute incomplete — much like how I felt,” she wrote. Her father advised her, “If that happens again, you draw your own box.”

Journalists have bridled at accusations that their coverage of the royal family has been tainted by racism, pointing out that British news outlets have always been free to criticize the royals, whose luxurious lifestyle is supported by public funds.

Among the sore points this year was the baby shower hosted by celebrity friends of the duchess in New York, a privately financed event that was said to cost 330,000 pounds, or more than $430,000.

“The clash comes when a free-spending American TV celebrity, the independent Ms. Markle, becomes the British queen’s granddaughter-in-law and joins soberer ornaments on the cracked marble mantelpiece of ancient royalty,” the journalist Libby Purves wrote in February in a column for The Times of London.

Last fall, the couple announced they would move out of Kensington Palace, in central London, and take up residence about 25 miles west of the British capital in newly refurbished quarters: Frogmore Cottage, near Windsor Castle. There have been rumors that the couple could be dispatched in the next few years on an extended tour of Africa, where 19 nations, mostly former colonies, are members of the Commonwealth of Nations.

The duchess hinted of her hopes for her child when speaking on a panel for International Women’s Day in March, saying she expected it to be a feminist.

Citing a phrase she had seen in a documentary about “the embryonic kicking of feminism” during pregnancy, she said, “I loved that, so boy or girl, whatever it is, we hope that that’s the case with our little bump.”