The Queen will also meet staff, trustees and supporters of the Legion
The Queen will meet Afghanistan and Iraq veterans when she opens the Royal British Legion's new headquarters.
The personnel and their families have all been helped by the charity.
The opening of Haig House, in Borough, south London, will also be attended by broadcasters and Legion supporters Huw Edwards and Alastair Stewart.
The Legion, which was founded in 1921 and is famous for its annual Poppy Appeal, provides welfare support to the service community.
Sales of the paper flowers in 2007 raised Ł30m.
The organisation's new premises been equipped with modern facilitates for staff.
The Queen and the Duke of Edinburgh will also meet staff, trustees and supporters on their tour of the building.
Since 1947, the Legion had been based in Pall Mall, near St James' Palace in central London.
Its Director General Chris Simpkins said: "The Legion is not just about those who served in wars past but about campaigning and caring for current service personnel and their families.
"There has been a 30% increase in requests for help from those under the age of 35 and the Legion has risen to the challenge of meeting their needs thanks to the public's support."