Prince Harry says he is "thrilled" after announcing he is to marry US actress Meghan Markle.
The fifth in line to the British throne will marry Ms Markle early next year.
Prince Harry said he was "thrilled, over the moon," as he posed for photographs with his fiancee in the grounds of Kensington Palace in London.
Asked when he knew Markle was "the one", he replied: "The very first time we met."
In their first broadcast interview after announcing the news, Prince Harry and Ms Markle held hands as they discussed the moment of their proposal and their courtship.
Ms Markle said the couple were having a cosy night at Nottingham Cottage in the grounds of Kensington Palace, over roast chicken dinner.
"It was so sweet and natural, and very romantic. He got on one knee," Ms Markle said. "I could barely let you finish proposing. I said, 'Can I say yes now?'"
Just four weeks after a blind date in July 2016 that left him "beautifully surprised", Prince Harry took his wife-to-be on a trip to Botswana to camp under the stars in his tent.
He said that he had not watched the show which made Ms Markle's name, and Ms Markle too was relatively unfamiliar with Britain's royal family before meeting Harry.
"I had never watched Suits, I had never heard of Meghan before and I was beautifully surprised when I walked into that room and saw her. I was like, 'OK well I'm going to have to really up my game here'," Harry said.
Ms Markle said she was not prepared for the level of attention their relationship would get.
"I did not have any understanding of just what it would be like," she said, saying there was a misconception that because she was an actress she would be used to being in the media spotlight.
Prince Harry and Ms. Meghan Markle are "thrilled and happy" to be engaged. pic.twitter.com/HBz30SbZVE— Kensington Palace (@KensingtonRoyal) November 27, 2017
Kensington Palace said Ms Markle's engagement ring was designed by Prince Harry and features two diamonds which belonged to his late mother, Diana, Princess of Wales.
At the centre of the ring is a diamond from Botswana. The band is made from gold.
Prince Charles also said he was "thrilled", adding that Ms Markle's parents had given their blessing.
Prince Harry had already told the Queen and "other close members of his family" of the engagement, which took place in London earlier this month, Prince Charles said on Twitter.
The announcement, issued by Clarence House, the Prince of Wales and Duchess of Cornwall's official residence, said details about the wedding day would be unveiled "in due course".
The Prince of Wales is delighted to announce the engagement of Prince Harry to Ms. Meghan Markle. pic.twitter.com/zdaHR4mcY6— Clarence House (@ClarenceHouse) November 27, 2017
The Queen and Duke of Edinburgh said they were "delighted for the couple and wish them every happiness", a Buckingham Palace spokesman said.
Prince William and Catherine, Duchess of Cambridge, said they were "very excited for Harry and Meghan", adding: "It has been wonderful getting to know Meghan and to see how happy she and Harry are together."
Ms Markle's parents, Thomas Markle and Doria Ragland, said their daughter was a "kind and loving person" and they were "incredibly happy".
They added: "To see her union with Harry, who shares the same qualities, is a source of great joy for us as parents.
Prince Harry, 33 and Ms Markle, 36, made their first public appearance as a couple in September at the opening ceremony of the Invictus Games, a sporting event set up by the prince for injured, wounded and sick soldiers.
Prince Harry first confirmed his relationship with Ms Markle in November 2016, in a statement from Kensington Palace attacking the media for subjecting her to a "wave of abuse and harassment".
That statement said the couple were "a few months into a relationship" and it was "not right" that Ms Markle should receive such treatment.
In his office's warning to the media, Prince Harry referred to the sexism and racism directed at ms Markle, whose father is white and her mother African-American.
"Any the end of day I'm really just proud of who I am and where I come from and we have never put any focus on that," she said in the BBC interview. "We were just hit so hard at the beginning with a lot of mistruths."
It described nightly legal battles to keep defamatory stories out of papers, attempts by reporters and photographers to get into her home and the "bombardment" of nearly every friend and loved one in her life.
Ms Markle spoke about her love for the prince for the first time in September - telling Vanity Fair magazine: "We're two people who are really happy and in love".
She said the pair were enjoying a "special" time together, adding: "I'm sure there will be a time when we will have to come forward and present ourselves and have stories to tell, but I hope what people will understand is that this is our time."
Ms Markle may not have been a familiar name in the UK until recently, but in the US she was known for her role as Rachel Zane in TV legal drama Suits.
She was born in Los Angeles in 1981. Her father was a TV lighting director for soaps and sitcoms and her mother a clinical therapist.
She attended a private primary school before studying at a girls' Roman Catholic college and later graduating from Northwestern University School of Communication in 2003, just as her acting career was beginning.
Until recently, a union with Ms Markle would have ruled Prince Harry out of succeeding to the throne - due to her being a Roman Catholic.
New rules on royal succession came into force in 2015, allowing members of the Royal Family to marry a Roman Catholic and become king or queen.
In 2011, she married film producer Trevor Engelson but they divorced two years later. The Church of England agreed in 2002 that divorced people could remarry in church at the discretion of the priest.
Like Prince William's wife, Ms Markle will not become a princess in her own right after the marriage. However, Prince Harry, like his brother, is likely to be made a duke when he marries, meaning Ms Markle would become a duchess.
Their married home will be the prince's current residence, Nottingham Cottage, on the grounds of Kensington Palace - where the Duke and Duchess of Cambridge, with Prince George and Princess Charlotte, also have an apartment.
- BBC / Reuters