Many will rise early in the United States to watch the noon (7 a.m. ET) ceremony in which Harry, long a favorite with the British public for his irreverent good humor, will tie the knot with his California-born bride.
Thousands more are expected to line the streets of Windsor in hope of catching a glimpse of the royal newlyweds as they process through the town in an elegant horse-drawn carriage.
The ceremony and two receptions will bring together Britain’s most senior royals, including Harry’s grandparents, the Queen and Prince Philip, and Prince Charles, with a raft of UK and US celebrities. It will be Prince Philip’s first public appearance since he had hip surgery last month.
The wedding also represents a historic moment for the royal family, as it welcomes an outspoken biracial, American divorcée into its ranks.
Some 1,200 ordinary members of the public have been invited to watch from within the grounds of Windsor Castle as the couple’s 600 or so guests arrive at St. George’s Chapel.
Meghan and Prince Harry will travel to Windsor separately, having spent Friday night at different luxury hotels. While Markle made her final preparations in the company of her mother, Doria Ragland, Harry spent the evening with his brother and best man, Prince William.
Markle, 36, will be supported on her way to the chapel by Ragland. She will then meet her gaggle of bridesmaids and page boys, who include Harry’s four-year-old nephew Prince George and three-year-old niece Prince Charlotte, as well as Markle’s godchildren.
The world will get its first full glimpse of the wedding dress when Markle steps out of a car by the chapel’s West Steps. The designer has been kept a closely guarded secret, prompting months of speculation.
There will be many royal wedding firsts, as the couple has decided to break with custom on several fronts.
Meghan has decided not to be chaperoned for much of the procession down the aisle, a move that is unprecedented for a royal bride in Britain and can be seen as a bold feminist statement.
She will be accompanied in this first part of the wedding procession only by her six bridesmaids and four page boys, with a senior church figure walking ahead.
Prince Charles will join her when she reaches the Quire — where the main royal guests are seated — and will walk her down the Quire aisle to the foot of the altar.
There, she will be met by Harry. As a military veteran and Captain General of the Royal Marines, he is likely to wear ceremonial uniform, as did William on his wedding day.
Harry and Meghan will then say their vows in front of their guests and a TV audience of potentially millions around the world.
The order of service will have a distinctly modern feel. The couple has chosen a modern set of wedding vows, and the text of the formal parts of the service are taken from Common Worship, the Church of England’s standard liturgy, first published in 2000. It is thought to the the first time that this text has been used in a royal wedding.
The introit music, Handel’s “Eternal Source of Light Divine,” will be sung by soprano Elin Manahan Thomas, and the Kingdom Choir, a group of 20 gospel singers, will perform the Ben E. King classic “Stand By Me.” The ceremony will end with the orchestra playing “This Little Light of Mine,” a gospel song that became synonymous with the civil rights movement in the US.
The dean of Windsor, the Right Reverend David Conner, will conduct the service, while the Archbishop of Canterbury, Justin Welby, the most senior cleric in the Church of England, will officiate.
In a break with British royal custom — and in a nod to the bride’s homeland — American bishop Michael Curry, head of the Episcopal Church in the United States, will give the sermon.
After the hour-long ceremony, the newlyweds will emerge from the chapel by the West Door and make their way to the horse-drawn carriage which will carry them in procession through the streets of Windsor. There will be no shortage of military pageantry, with members of the Household Cavalry forming a staircase party and trumpeters playing as they make their exit.
Cheering crowds will greet the couple as they begin their first journey together as husband and wife, less than two years after they first met in London.