The Cenotaph is a monument to military personnel killed in active service. It is the site of the United Kingdom's national day of remembrance, Remembrance Sunday.

The word cenotaph comes from the Greek 'cenos', meaning empty, and 'taphos', meaning tomb. It therefore signifies a tomb or monument to a person or a number of people whose remains are elsewhere; most commonly, they are the victims of war.

The Cenotaph in London was designed by the celebrated architect Sir Edwin Lutyens and constructed from 1919 to 1920 in Portland stone. It is in fact an identical copy of an earlier Lutyens cenotaph built at the same site and constructed for the Allied Victory Parade at the end of World War I, in 1919. This earlier monument was commissioned by the then Prime Minister David Lloyd George and was built from wood and plaster.

The Cenotaph is decorated only with a carved wreath on each end and the words 'The Glorious Dead', chosen by poet and novelist Rudyard Kipling, most famous for his children's work 'The Jungle Book'.

Although at first glance the four sides of the Cenotaph appear to make a square, they are not exactly parallel and if extended would meet at a point about 1 mile above the ground.

Lutyens had originally wanted stone flags to be carved, but he was overruled and cloth flags now surround the Cenotaph. The flags displayed represent the Royal Navy, the British Army, the Royal Air Force and the Merchant Navy.

On Remembrance Sunday (the closest Sunday to Armistice Day, November 11), a service of remembrance for the war dead is held at the cenotaph and a minute's silence is observed at 11am (the 11th hour of the 11th day of the 11th month). Uniformed personnel file past the Cenotaph and salute as they pass. The Cenotaph was, notably, the only recipient of a salute from the driver of Princess Diana's funeral carriage during her funeral procession; on that occasion the driver did not even salute the Queen.