The Queen's husband Prince Philip will take part in his final public meeting before he officially retires from royal duties.
The 96-year-old announced his retirement in May, after decades of supporting the Queen, as well as attending events for his own charities and organisations.
Prince Philip is also known as the Duke of Edinburgh, but who is he and why is he so important?
The Duke of Edinburgh is the Queen's husband - they've been married for nearly 70 years.
They met while Prince Philip was an officer in the Navy during World War Two.
He and the Queen have four children: Prince Charles, Prince Andrew, Prince Edward and Princess Anne.
Prince Philip is also the grandfather of Princes William and Harry, and the great-grandfather of Prince George and Princess Charlotte.
Although he isn't the king, his job title is pretty special. He's the Queen's 'consort' - and his role is to support Queen Elizabeth II.
He now holds the record for the longest-serving consort in British history!
Prince Philip was born in 1921 on the Greek island of Corfu.
His family left Greece when Philip was just a one-year-old baby.
He spent his childhood in France, Germany and then here in Britain.
He celebrated his 96th birthday in June 2017.
Philip gave up his job in the Navy after Queen Elizabeth II's father died and she became Queen.
He has always thrown himself into his role of supporting her and has found a real passion in doing charity work.
One issue he cares about a lot is wildlife conservation - something he spoke to Newsround about back in 1986.
You may also have heard of one of his most important and famous charities: The Duke of Edinburgh Award scheme.
It offers challenges and adventure to thousands of young people in the UK.
Since the Duke of Edinburgh's Award was launched in 1956, millions of young people have taken part in the scheme.
Philip also has a reputation for speaking his mind, and sometimes his comments have caused some people embarrassment.
However, he is also praised by many for his dedication and his unique way of doing things.
The Queen is not only the head of state of the UK but she's also Head of the Commonwealth - an association of 52 countries, many of which used to be part of the British Empire.
As well as visiting parts of the UK, part of the Queen's job involves visiting these other countries, meeting people and doing lots of charity work, which Prince Philip often helps her with.
Since 1952, Prince Philip has completed 22,219 royal engagements on his own.
Every year the Royal Family carry out over 2,000 official visits throughout the UK and worldwide.
As the Queen and the Duke have become older more of these royal duties have been passed to the younger members of the family.
While Prince Philip's diary of events will come to an end in August, Buckingham Palace has said he may still decide to attend certain events alongside the Queen in the future.
The Queen's public schedule will continue as normal.