The Queen has been "a rock of strength" for the country and the world, David Cameron has said.
The Prime Minister will lead MPs in celebrating the Queen's 90th birthday. He will highlight the "extraordinary times" during her long reign, as the Commons pays tribute to the monarch.
Labour leader Jeremy Corbyn - a staunch republican - has said he's also looking forward to wishing the Queen a happy birthday.
The whole country will want to wish the Queen a happy birthday today - she has been a rock of strength for our nation.
-- David Cameron (@David_Cameron) April 21, 2016
Cameron is expected to say: "Her Majesty The Queen has lived through some extraordinary times in our world.
"From the Second World War to the rations with which she bought the material for her wedding dress.
"From presenting the World Cup to England at Wembley in 1966 to man landing on the moon three years later.
"From the end of the Cold War to peace in Northern Ireland.
"Throughout it all, as the sands of culture shift and the tides of politics ebb and flow, Her Majesty has been steadfast - a rock of strength for our nation, for our Commonwealth and on many occasions for the whole world.
"As her grandson, Prince William, has said: 'Time and again, quietly and modestly, the Queen has shown us all that we can confidently embrace the future without compromising the things that are important'."
But the monarch will have to wait for her birthday present from her ministers.
Cameron's official spokeswoman said that the Cabinet had agreed to give the Queen a present on her official birthday - on June 11.