In keeping with tradition, the Queen will lie in state before her funeral in London, which will allow members of the public to pay their last respects.
The solemn and historic occasion is expected to attract hundreds of thousands of people, and involves a huge coordinated security operation.
The Queen's death in Scotland also means there will be a second, smaller Lying at Rest there.
Here's all you need to know about the Queen’s Lying in State.
When and where is the Queen lying in state?
Queen Elizabeth II's coffin will lie in two locations across the coming days, where the public can pay their respects.
The first will take place at St Giles' Cathedral, in Edinburgh, and will be a smaller ceremony where the Queen will lie at rest. It will begin on Monday, September 12.
Scotland’s government has said members of the public will be able to file past the coffin from around 5.30pm on Monday until Tuesday (September 13) afternoon at around 3pm.
Her Majesty’s coffin will be guarded by Vigils from The Royal Company of Archers, to allow the people of Scotland to pay their respects.
The Crown of Scotland will also be placed on top of the Queen's coffin while it rests at the cathedral.
Her coffin will then be flown to London ahead of it lying in state at Westminster Hall from Wednesday, September 14.
Here, her Majesty will lie in state for four days until the day of her funeral on Monday, September 19.
There will first be a ceremonial procession through London, taking in Queen’s Gardens, The Mall, Horse Guards and Horse Guards Arch, Whitehall, Parliament Street, Parliament Square and New Palace Yard.
After the coffin's arrival at Westminster Hall, the Archbishop of Canterbury will conduct a short service, which will be attended by members of the Royal Family.
Once that service ends, there will be the opportunity for politicians and dignitaries to pay their respects to the Queen.
Westminster Hall will then be opened to the public for 24 hours a day, starting from 5pm on Wednesday until 6.30am the following Monday.
Preparations are underway around Westminster to make way for the lengthy queues
The Queen’s coffin will be guarded around the clock by a vigil of units from the Sovereign’s Bodyguard, the Household Division, or Yeoman Warders of the Tower of London.
Traditionally, lying in state begins five days after the day of death - known operationally as D+5.
The Queen died on Thursday, September 8, but because the announcement came relatively late - around 6.30pm - plans were moved by a day to allow time for the complex arrangements to be made.
Where is Westminster Hall?
Westminster Hall, which dates back to 1099, is in the Palace of Westminster and is the oldest building on the Parliamentary estate.
It forms part of the Westminster Unesco World Heritage Site and the UK Parliament website refers to its “great size”, the “magnificence” of its roof, and its central role in British history.
The building has been the site of key events, such as the trial of Charles I, coronation banquets, and addresses by world leaders.
Will there be a queue?
Yes - government guidance says that the queue is expected to be very long.
People will need to stand for “many hours, possibly overnight” with very little opportunity to sit down as the queue will be continuously moving.
A queue route map for mourners wishing to pay their respects to the Queen as she lies in state has been released.
The queue to Westminster Hall is expected to stretch for about four miles along the River Thames, the newly published route reveals.
The miles-long queue will begin on the Albert Embankment by Lambeth Bridge and will continue along the South Bank to Southwark park in Bermondsey, south east London.
From Albert Embankment, the queue will run along Belvedere Road behind the London Eye, and head onto the South Bank where it will follow the River Thames past the National Theatre, Tate Modern and HMS Belfast under Tower Bridge and along to Southwark park.
Once people reach the front of the queue at Albert Embankment, they will be directed across Lambeth Bridge, into Victoria Tower Gardens and through airport-style security before entering the Palace of Westminster where the Queen will be lying-in-state.
More than three quarters of a million people are expected to descend on Westminster to pay their respects to the Queen.
People have already begun queuing, despite the Lying in State not opening to the public until 5pm on Wednesday, 14 September.
As large crowds are expected, there are likely to be road closures and delays on public transport.
How long will I be queuing for?
Government guidance stated: “Please note that the queue is expected to be very long. You will need to stand for many hours, possibly overnight, with very little opportunity to sit down, as the queue will keep moving.”
Queues are expected to stretch for as long as five miles.
As a result, it’s also asked people to think carefully about whether to take youngsters with them.
“Please consider this before you decide to attend or bring children with you,” the guidance added.
Can I attend if I’m disabled?
Step-free and accessible options are available for those who need them.
Will security be tight?
Visitors will go through airport-style security and there are tight restrictions on what you can take in, with people allowed just one small bag with one simple opening or zip.
Queue-jumpers and anyone drunk will be booted out of the queue by stewards and police patrolling the lines.
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Is there anything I need to bring?
Official guidance suggests that people should bring suitable clothing for the weather, food and drinks to have while queueing, a portable power bank for your mobile phone and any essential medication.
Are any items banned?
Yes. There is a list of banned items which includes flowers or other tribute items, including candles, soft toys, and photographs.
Other banned items include banners, flags, hampers, blankets, sleeping bags, folding chairs and camping equipment.
What should I wear?
Guidelines set out by the government have urged those who wish to attend to “dress appropriately for the occasion to pay your respects”, banning clothes “with political or offensive slogans”.
Visitors are also advised to plan ahead and wear weather appropriate clothing.
Can I film or take photographs?
The government guidance says people should not film, photograph, use mobile phones or other handheld devices in the security search area or within the Palace of Westminster.
Will there be somewhere to store larger bags?
A bag drop facility is available but capacity is limited, and there is no guarantee that there will be space at the facility.
Only bags smaller than 40cm x 30cm x 20cm will be allowed into the hall.
Waiting for bag storage space to become available will increase your queuing time.
What can people expect to see?
The closed coffin will be draped in a royal flag, usually a personal standard, and will rest on a raised platform called a catafalque, flanked by a military guard around the clock.
A priceless crown and other regalia are traditionally placed on top of a sovereign’s coffin.
Will the Royal Family be there?
It is likely that the Queen’s children or even grandchildren will honour her with a vigil and join the guard over the coffin at some point - a tradition which has been called the Vigil of the Princes.
Should the Princess Royal stand guard for the Queen, she will be the first female member of the royal family to do so.
What does it mean to lie in state?
Lying in State is a formality in which the closed coffin is placed on view, allowing the public to pay their respects before the funeral ceremony.
It is traditionally reserved for the Sovereign, current or past Queen Consorts, and occasionally other distinguished figures, such as former prime ministers.
During this time, the coffin rests on a catafalque in the middle of Westminster Hall, where it is guarded 24 hours a day.
The tradition stretches back to the 17th century, when Stuart sovereigns lay in state for a number of days.
The last person to lie in state in the UK was Queen Elizabeth The Queen Mother.
The Queen Mother had a ceremonial funeral, rather than a state funeral, but both can include a Lying in State.
An estimated 200,000 people visited Westminster Hall to pay their respects before her funeral on April 9, 2002.
The Duke of Edinburgh did not lie in state before his funeral on April 17, 2021 - a decision that was taken "in line with custom and with His Royal Highness’s wishes," according to officials.
Furthermore, the coronavirus pandemic and the restrictions in place at the time meant that mass public gatherings were not permitted.
Other notable figures who lay in state include Sir Winston Churchill before his state funeral in 1965.
What are the operations in place for the Queen's lying in state?
Operation Marquee covers the four days of the Queen's lying in state, focusing on the arrangements inside Westminster Hall, including ceremonial aspects, services and vigils.
Operation Feather deals with logistics outside Westminster Hall, including arrangements for the public. Thousands of people will queue in the streets as they wait to see the monarch's coffin on its catafalque.