Southsea Castle Lighthouse is located on the western ramparts of Southsea Castle. It guided vessels through the deep water approaches to Portsmouth Harbour.
The castle was the last of the coastal defences built for Henry VIII in 1544. The fortress defended against invasion from France and the Holy Roman Empire. It also defended the approaches to the Solent and the Royal Naval base at Portsmouth.
Located on the southern end of Portsea Island, Southsea Castle was significantly restored in the 1820s. During the refurbishment, a lighthouse was built at the castle at the request of the Admiralty. It was sited on the northern side of the western ramparts on the gun platform and built into the outer wall.
The lighthouse at Southsea Castle displayed three fixed sector lights. Initially, red and white sectors were shown, but later this changed to red and green from 1854 when its height was raised. The sector lights guided vessels through the safe water channel between Spitsand Fort and Horse Sand Forts.
The lighthouse keeper lived within the castle.
The lighthouse was discontinued in 2017 and replaced by a new structure within the harbour. This was established following changes to the harbour approaches to allow for the new aircraft carriers.