The 88-year-old monarch was to lay a wreath at the Cenotaph national war memorial in London, accompanied by senior members of the royal family and prime ministers past and present.
The centrepiece of a series of events marking the centenary of the outbreak of World War I, the ceremony's most solemn moment will be a two-minute silence from 1100 GMT.
The silence will start and end with a round from a 13-pounder World War I gun.
Prime Minister David Cameron said this year's Remembrance Sunday was "particularly poignant" as 2014 marked the centenary of the start of World War I, the 70th anniversary of the Normandy landings and the end of Britain's combat role in Afghanistan.
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"Today we stand united to remember the courageous men and women who have served our country, defended our freedoms and kept us safe," he said.
"We owe each and every member of our armed forces and the families who support them a tremendous debt -- one that can never be repaid -- and I pay huge tribute to their bravery and resolve."
Queen Elizabeth was to be joined by her husband Prince Philip, 93, who was a naval officer in World War II, and their eldest son Prince Charles, the heir to the throne.