Some 1,900 guests will be at the wedding of Prince William and Kate Middleton, St James's Palace has said.
No names have officially been released as invitations begin arriving but more than half are family and friends.
UK and foreign dignitaries, senior politicians, charity workers and celebrities like the Beckhams are said to be among the Westminster Abbey congregation on 29 April.
Not all the guests at the service will go on to a Buckingham Palace reception.
The BBC's royal correspondent Peter Hunt says individuals who have come into contact with Prince William will also be present, including people who have been homeless and soldiers injured in Afghanistan and Iraq.
Some famous names on the guest list, such as David and Victoria Beckham, have already trickled out, our correspondent added.
The service will be conducted by the Dean of Westminster, with the Archbishop of Canterbury marrying the prince and his bride.
Seated in the front pews will be the Queen, the Duke of Edinburgh, the Prince of Wales, Duchess of Cornwall and best man, Prince Harry.
Alongside them will be Kate's parents, Michael and Carole Middleton, Kate's sister and maid of honour, Pippa, and her brother James.
About 600 relatives, friends and dignitaries are invited to the lunchtime reception hosted by the Queen at Buckingham Palace to toast the couple, who got engaged in October while on holiday in Kenya.
And just 300 will stay on at the palace for a more intimate evening dinner, which will be followed by dancing.
In the past few days, those on the guest list have been opening their invitations - a white card gilded with gold in a pale brown envelope.
The Queen's initials are die-stamped in gold on the card below a crown.
It reads: "The Lord Chamberlain is commanded by the Queen to invite [name] to the marriage of his Royal Highness Prince William of Wales KG with Miss Catherine Middleton at Westminster Abbey on Friday 29 April 2011 at 11.00am."
Guests are asked to reply to the Lord Chamberlain's office which is handling the ceremonial and formal parts of the preparations.
The dress requirements are given as "uniform, morning coat or lounge suit".
The choice of guests who will get to watch the couple exchange vows at the abbey, reflects William's position as second-in-line to the throne.
They will include more than 200 members of the government, parliament and diplomatic corps, as well as 60 governors-general and prime ministers from Commonwealth countries.
The prince also has a number of charitable interests, including the homeless organisation Centrepoint, wildlife conservation group, Tusk Trust and the Royal Marsden Hospital. Some 80 representatives will be drawn from charities.
The guest list also includes 30 members of the armed forces as well as representatives from the Church and other faiths.
A spokesman for the Duchess of York confirmed she had not been invited to the wedding.
"She wasn't and she never thought she would be.
"She won't be attending and she was never expecting to attend. She's going to be overseas at the time," he said.
David Beckham's spokesman would not confirm whether he and Victoria were invited.
"We're not discussing it," he said, adding that it was a private matter.