Guests including Prince Harry's uncle Earl Spencer, Oprah Winfrey and George Clooney have arrived at St George's Chapel for the royal's wedding to Meghan Markle.
Ahead of the ceremony, due to take place at the Windsor Castle chapel at noon, it was announced that Harry and his American bride will be known as the Duke and Duchess of Sussex.
Other information to be released includes details of the couple's wedding rings - Harry's is a platinum band with a textured finish, while Meghan's has been fashioned from a piece of Welsh gold, gifted by the Queen.
READ MORE: ROYAL WEDDING: Key timings and details for Prince Harry and Meghan Markle’s big day
Among the early arrivals for the ceremony were Earl Spencer, in a morning suit, and talk show host Winfrey, who is dressed in a pale pink suit, matching hat and sunglasses.
Winfrey was spotted talking to actor Idris Elba, while singer James Blunt has also been seen taking his place.
Actor George Clooney and his barrister wife Amal were also among the arrivals, as were football hero David Beckham and his wife Victoria.
Community Champions invited to share in the couple's big day - including charity workers, local volunteers and community stalwarts - also filed into the castle grounds with hampers ready to enjoy the celebrations.
Hours before the ceremony, Buckingham Palace announced that Harry has been given a dukedom - the highest rank in the British peerage - and Meghan will become Her Royal Highness the Duchess of Sussex.
The Queen's grandson, who is sixth in line to the throne, will pledge to love, comfort, honour and protect the former actress as they become husband and wife in the historic surrounds of St George's Chapel.
Harry also received Scottish and Northern Irish titles, becoming the Earl of of Dumbarton and Baron Kilkeel, which means Meghan will become the Countess of Dumbarton and Baroness Kilkeel.
Tens of thousands of royal fans have begun to descend on the Berkshire town to catch a glimpse of the bride and groom, as police have effectively created a ring of steel around the castle in a massive security operation.
Weather forecasters are expecting wall-to-wall sunshine, meaning the newlywed couple will be able to ride through Windsor town centre in the open top Ascot landau for their carriage procession.
Some 250 members of the armed forces will take part in the pomp and ceremony of the celebrations, with regiments closely connected to former soldier Harry lining the streets.
Meghan will emerge from the hour-long televised ceremony, which begins at noon, as an HRH and a member of the British royal family after saying her vows.
Harry spent his last night as a single man at the exclusive Coworth Park country house hotel in Ascot.
Meanwhile 15 miles away, Meghan stayed with her mother Doria Ragland at the luxury Cliveden House Hotel in Taplow, Berkshire.
Around 30 members of the royal family including the Queen and the 96-year-old Duke of Edinburgh, who is well enough to attend after undergoing a recent hip operation, will gather in the 600-strong congregation.
The Archbishop of Canterbury, who will marry Harry and Meghan, has spoken of the strong bond the couple share.
"There's profound affection between them which is wonderful and a deep understanding and mutual support," he said.
"You see in the way they respond to each other, caring for each other, which is something you see in many couples but not always."
As the Order of Service was published on the morning of the wedding, it revealed Harry will wear a ring - not a given for royal men - and Meghan will not promise to obey her husband in the vows.
The moving, soul classic Stand By Me by Ben E King will be performed by Karen Gibson and The Kingdom Choir, with the gospel singers also delivering Etta James' uplifting version of Amen/This Little Light of Mine - a favourite in African-American churches.
The presiding bishop of the American Episcopal Church Bishop, Michael Curry will give the address.
The Prince of Wales will take on the role of the absent father of the bride Thomas Markle, and walk his future daughter-in-law through the Quire up the altar to meet her groom.
There will be sadness amid the joy for Meghan with her father missing her big day.
The reclusive former TV lighting director will be thousands of miles away in Mexico after pulling out of attending on medical advice with just two days to go after undergoing heart surgery.
Harry too will be thinking of his late mother Diana, Princess of Wales, who died in car crash when he was 12.
He has invited her three siblings, Earl Spencer, Lady Sarah McCorquodale and Lady Jane Fellowes, as a way of honouring her.
Lady Jane is giving a reading.