Haslar Marina is a large, modern marina situated in Gosport on the western side of Portsmouth Harbour, just inside the harbour entrance and opposite Portsmouth's Historic Dockyard.

It lies within the sheltered waters of Haslar Lake and Creek, offering deepwater access with no tidal restrictions. The marina is easily identified by its iconic green lightship, "Mary Mouse II," visible from the harbour approach.

Following a significant redevelopment completed in 2023, the marina accommodates hundreds of berths and caters for vessels of considerable size.

It is part of the Boatfolk group and is accessible by sea, road, rail, or on foot, with straightforward navigation directly from Portsmouth Harbour's main Boat Channel.