She joined 9,000 veterans, military personnel and senior politicians at the country's biggest service in London's Whitehall.
Tens of thousands took part in similar ceremonies at towns and villages across the country, while British troops in Iraq and Afghanistan held services to remember the fallen.
At 11 am, a single cannon shot marked the start of the silence as Big Ben struck the hour at the Palace of Westminster. A second shot ended the silence as buglers from the Royal Marines sounded the Last Post.
The Queen, wearing a black coat and black hat, laid the first wreath of red poppies at the Cenotaph, the Portland stone memorial bearing the words ''The Glorious Dead''.
Following her were Prime Minister Tony Blair, Conservative leader David Cameron and the Liberal Democrats' leader Sir Menzies Campbell. Chancellor Gordon Brown and former prime ministers John Major and Margaret Thatcher also attended.
Representatives of the Commonwealth countries placed tributes at the memorial and veterans paraded past the monument.
''WE WILL REMEMBER THEM'' The widow of an officer killed in Iraq laid a wreath of autumn leaves on behalf of the families and friends of all those killed on duty since World War Two.
Mother-of-two Raqual Harper-Titchener's husband Major Matthew Titchener was one of three military policemen killed while on patrol in the southern city of Basra in August 2003.
''It is a great privilege and honour to be here today to remember Matt, and all those brave men and women who have been killed on duty,'' she said.
A red poppy with the words ''We Will Remember Them'' was projected onto the funnel of the Royal Navy's flagship aircraft carrier HMS Illustrious, moored at Greenwich, southeast London.
The widow of Lieutenant Commander Darren Chapman, who died in a helicopter crash in Basra in May, paid tribute to her husband at a service on the ship.
''His loss is something we feel deeply every day,'' said Elizabeth Chapman, who was accompanied by her son Ben, 13, and daughters Chloe, 16, and Georgina, eight.
REUTERS AKJ PM1725