The Queen will attend cabinet in Downing Street on Tuesday, becoming the first monarch to attend the briefing since Queen Victoria.
The Queen will be there as an observer and receive a gift to mark her Diamond Jubilee.
She is to become the first monarch to attend the weekly briefing since Queen Victoria in the 19th century, Downing Street said. She will be seated next to Prime Minister David Cameron during the meeting.
The announcement was made by Mr Cameron on Twitter.
The Queen will visit Downing St tomorrow. She will be presented with a gift to mark her Diamond Jubilee and attend Cabinet as an observer.— No. 10 Press Office(@Number10press) December 17, 2012
"I think she will sit round the table and I think she will sit alongside the prime minister. She is attending as an observer because she is not a member of the cabinet," Mr Cameron's spokesman said.
The Queen has had a relationship with 12 prime ministers - eight Conservative and four Labour - over the past 60 years, including Sir Winston Churchill, who told her at their first audience that he could advise her from a lifetime of experience but that a time would come when she would advise prime ministers younger than herself from a similar standpoint.
The first of those leaders younger than the Queen was John Major. Mr Cameron was not even born when the Queen acceded to the throne. He is the youngest of the Queen's prime ministers, and it is Mr Cameron who will deal with law regarding primogeniture enabling any future daughter of the Duke and Duchess of Cambridge to become queen before any younger brothers.
The change has been agreed by the Queen, the prime minister and all Commonwealth prime ministers.
Downing Street would not disclose details about the gift.
The Queen previously visited Downing Street in July with four of the prime minister who have served during her reign including Mr Cameron, Sir John Major, Tony Blair and Gordon Brown.