Portsmouth Harbour railway station is a railway station in Portsmouth, England. It is situated beside Gunwharf Quays in the city's harbour, and is an important transport terminal, with a bus interchange and ferry services to Gosport and the Isle of Wight. The station currently has four platforms in use: numbered 1, 3, 4 and 5. It is managed by South Western Railway. Platform 2 is no longer in use, having been decommissioned in the early 1990s following major repair and refurbishment work to the pier that the platforms sit on. The station is located adjacent to Portsmouth Harbour between the Gunwharf Quays shopping centre and the Historic Dockyard. Unusually for a mainline railway station, it is built over water as the station was originally constructed on wooden piles, which were later replaced by iron supports.

Portsmouth Harbour is a 1,264.2-hectare (3,124-acre)/12.6 km2 (4.9 sq mi) biological Site of Special Scientific Interest between Portsmouth and Gosport in Hampshire. It is a Ramsar site and a Special Protection Area.