Guests - including veterans and celebrities - are arriving at Windsor Castle for the wedding of Prince Harry and Meghan Markle.
Among the 600 guests are Oprah Winfrey, George and Amal Clooney, David and Victoria Beckham and Jonny Wilkinson.
The couple will wed at noon in St George's Chapel before travelling through the town.
Prince Harry has been given the title of Duke of Sussex ahead of his marriage, with Meghan Markle becoming the Duchess of Sussex after the wedding, Buckingham Palace has announced.
He will also gain the Scottish title, the Earl of Dumbarton, and the title of Baron Kilkeel.
Millions of people around the world are set to watch the wedding of Meghan Markle and Prince Harry in Windsor.
Hundreds more have spent a night on the streets of Windsor to secure the best viewing spot.
The couple will wed at noon at St George's Chapel in Windsor Castle, before travelling through the town in a carriage.
In her vows, Ms Markle will not promise to "obey" her husband and Prince Harry has chosen to have a wedding ring.
Prince Charles will walk Ms Markle down the aisle, after her father, Thomas, is unable to attend for health reasons.
On the eve of their wedding, Prince Harry told crowds in Windsor he was feeling "relaxed" and Ms Markle said she was feeling "wonderful".
Crowds of well-wishers - many wearing union flags - and the world's media have been gathering in Windsor in the week leading up to the big day.
As many as 100,000 people are expected to line the streets, hoping to get a glimpse of the happy couple.
Nicky and Matt Pruner, from the United States, extended their holiday to be in Windsor for the wedding.
Mrs Pruner said: "I camped out all night at Kate and William's wedding and I said I would never do it again - and here I am."
Mr Pruner said: "It feels like a festival, except this one has a meaning. It just gives hope to the world."
Six-hundred guests will be present at the wedding, officiated by the Archbishop of Canterbury, Justin Welby. The service broadcast to millions across the world.
About 1200 members of the public - many who are recognised for their charity work - have been invited to the wedding.