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.

A hydraulic accumulator is a pressure storage reservoir in which an incompressible hydraulic fluid is held under pressure that is applied by an external source of mechanical energy. The external source can be an engine, a spring, a raised weight, or a compressed gas. An accumulator enables a hydraulic system to cope with extremes of demand using a less powerful pump, to respond more quickly to a temporary demand, and to smooth out pulsations. It is a type of energy storage device.