Grimsby Dock Tower is a hydraulic accumulator tower and a maritime landmark at the entrance to the Royal Dock, Grimsby, in North East Lincolnshire, England. It was completed on 27 March 1852, based on William Armstrong's idea of the hydraulic accumulator, with the purpose of containing a 30,000-imperial-gallon (140,000 L) reservoir at a height of 200 feet (61 m), that was used to provide hydraulic power to power the machinery of the Grimsby Docks. The extreme height of the tower was necessary to achieve sufficient pressure, and as a result of this, the tower can be seen for several miles around, even far inland on the north bank of the Humber estuary in villages such as Patrington.

William George Armstrong, 1st Baron Armstrong, was an English engineer and industrialist who founded the Armstrong Whitworth manufacturing concern on Tyneside. He was also an eminent scientist, inventor and philanthropist. In collaboration with the architect Richard Norman Shaw, he built Cragside in Northumberland, the first house in the world to be lit by hydroelectricity. He is regarded as the inventor of modern artillery.