The Tower Hill Memorial is a pair of Commonwealth War Graves Commission memorials in Trinity Square Gardens, on Tower Hill in London, England. The memorials, one for the First World War and one for the Second, commemorate civilian, merchant seafarers and fishermen who were killed as a result of enemy action and have no known grave. The first, the Mercantile Marine War Memorial, was designed by Sir Edwin Lutyens and unveiled in 1928; the second, the Merchant Seamen's Memorial, was designed by Sir Edward Maufe and unveiled in 1955. A third memorial, commemorating merchant seamen who were killed in the 1982 Falklands War, was added to the site in 2005.

Tower Hill is the area surrounding the Tower of London in the London Borough of Tower Hamlets. It is infamous for the public execution of high status prisoners from the late 14th to the mid 18th century. The execution site on the higher ground north-west of the Tower of London moat is now occupied by Trinity Square Gardens.