Prince Harry is engaged to the American actress Meghan Markle, Clarence House announced on Monday morning.
The prince, 33, who is fifth in the line to the throne, proposed in London earlier this month to the 36-year-old Ms Markle.
The wedding is set to be in the spring of 2018.
In a statement Clarence House said the Prince of Wales, Harry's father, is 'delighted to announce' the engagement.
It added Harry had told the Queen and other members of his family and had also 'sought and received the blessing of Ms Markle's parents'.
The Archbishop of Canterbury joined the Prime Minister and others in congratulating the couple, saying he was 'absolutely delighted' by the news.
'I have met Prince Harry on a number of occasions and have always been struck by his commitment and passion for his charities, and his immense love for his family,' he said in a statement from Lambeth Palace.
'Marriage is a special and joyous commitment, one that Jesus celebrated together with friends at the wedding in Cana. I am so happy that Prince Harry and Ms Markle have chosen to make their vows before God.
'I wish them many years of love, happiness and fulfilment and ask that God blesses them throughout their married life together.'
Their 16-month relationship began when they met through mutual friends in London and they have been almost inseparable in recent months, making their first public appearance together in September.
The news will prompt wild excitement across the UK at the prospect of another royal wedding, which may be taken by the Archbishop of Canterbury. Such is the enthusiasm for the couple that Prince Harry has felt forced to issue an unprecedented rebuke to photographers and press attention, which he said had crossed a line.
A statement in November from his press spokesman said Markle 'has been subject to a wave of abuse and harassment' and condemned the 'the racial undertones of comment pieces; and the outright sexism and racism of social media trolls'.
It accused reporters of attempst 'to gain illegal entry to her home and the calls to police' as well as 'substantial bribes offered by papers to her ex-boyfriend'.
Harry's older brother William married Kate Middleton in Westminster Abbey and the expectation will be for Harry to follow suit although details for the wedding are yet to be announced.
The couple will live together in London after their marriage.
