Seaforth Dock is a purpose-built dock and container terminal, on the River Mersey, England, at Seaforth, to the north of Liverpool. As part of the Port of Liverpool and Liverpool Freeport, it is operated by the Mersey Docks and Harbour Company. Situated at the northern end of the dock system, it is connected to Gladstone Dock to the south, which via its lock entrance provides maritime access to Seaforth Dock from the river.

The River Mersey is a major river in North West England. Its name derives from Old English and means "boundary river", possibly referring to its having been a border between the ancient kingdoms of Mercia and Northumbria. For centuries it has formed part of the boundary between the historic counties of Lancashire and Cheshire.