Her Majesty's Naval Base (HMNB) Portsmouth is one of three operating bases in the United Kingdom for the British Royal Navy, (the others being HMNB Clyde and HMNB Devonport). Portsmouth Naval Base is part of the city of Portsmouth; it is located on the eastern shore of Portsmouth Harbour, north of the Solent and the Isle of Wight.

The base is home to the oldest dry dock in the world, as well as being the headquarters for two thirds of the Royal Navy's surface fleet. The base is also home to a number of commercial shore activities, including shipbuilding and ship repair (operated by BAE Systems); naval logistics, accommodation and messing; and personnel support functions (e.g. medical and dental; education; pastoral and welfare) provided by Defence Equipment and Support.

The base is the oldest in the Royal Navy and it has been an important part of the Senior Service's history and the defence of the British Isles for centuries. At one time it was the largest industrial site in the world.The Naval Base is also home to the "Portsmouth Historic Dockyard", which allows members of the public to visit important maritime attractions such as the Mary Rose, HMS Victory and HMS Warrior. - from Amzon