Thousands will be invited to the sit-down lunch on June 12, which will close one of the capital's best known roads to celebrate Queen Elizabeth's patronage of more than 600 charities and other groups.
Guests will receive a hamper-style lunch, with entertainment and Union flags, and more people will be able to share in the festivities at 'live sites' with big screens in Green Park and St James's Park nearby.
Tickets will be hard to come by for the public, but a lucky few can win a seat in a lottery-style ballot.
The Queen's having a party
Peter Phillips, the Queen's grandson, is helping to organise the street party in his role as director of Sports Entertainment Ltd, a global events agency which came up with the idea for The Mall street party.
Mr Phillips told the Press Association: "We wanted to create a celebration based off the back of the successful Golden Jubilee and Diamond Jubilee where there was a ground swell of warmth and affection for the Queen."
A mockup of what the party will look like
QUEEN'S BIRTHDAY STREET PARTY - WHO WILL BE INVITED?
The vast majority of people invited will be charity workers, and those who work for other organisations that The Queen is patron of - but there is a chance for members of the public to get a seat as well.
7,500 tickets will be given to guests from the Queen's charities and organisations. It is not yet clear how these will be allocated.
1,000 tickets will be made available for a public ballot, with details to follow.
1,500 tickets will be provided to the event's official partners, such as sponsors like Marks & Spencer
Much greater numbers of people are expected to picnic in Green Park and St James's Park nearby, watching the entertainment from The Mall on big screens. And the entire country will be encouraged to hold their own street parties and lunches to join in.
Phillips, the party's organiser, stressed next year's celebration would emphasise the Queen's support for her charities: "We want to reflect the service she's given to all her organisations and charities."
He added: "And insure there was a suitable celebration of her commitment to her patronages and provide the opportunity for her patronages and other communities around the country to say thank you."
Princes William and Harry will act as 'joint presidents' of the party.
The event takes place around the Queen's official birthday, celebrated in June. Her actual birthday is on April 21.
The not-for-profit event will also raise money for a newly created Patron's Fund, which will be used to support specific initiatives and projects run by the Queen's charities.
The Queen is patron of a wide range of organisations from Barnardo's and Battersea Dogs and Cats Home to the British Diabetic Association and Great Ormond Street Hospital.
The monarch also has an official role with organisations in the Commonwealth like the Australian Medical Association, Canadian Red Cross Society and the New Zealand Medical Association.
The organisers hope communities around the country will be inspired to stage Patron's Lunches in their own areas and raise money for local projects.
The Queen with her grandson and great-grandson, Prince William and Prince George
Elizabeth's 'lifetime dedication to service' will be marked with a series of other events next summer to mark her official birthday.
In may, there will be four events inside the grounds of Windsor Castle.
A service of thanksgiving attended by the Queen and Philip will be held at St Paul's Cathedral on Friday, June 10, the following day the traditional Trooping the Colour ceremony, also known as the Queen's Birthday Parade, will be staged in Horse Guards Parade and on the Sunday the street party.