HMS King Alfred is a Royal Naval Reserve shore establishment in Portsmouth, England. The unit has a complement of over 200 reservists and provides training facilities to other lodger units, including the local Royal Marines Reserve (RMR) City of London (Portsmouth Detachment), and local University Royal Naval Unit (URNU). HMS King Alfred previously opened on 1 April 1994 on Whale Island and was commissioned on 8 June that year, replacing the closed units at and . In April 2021, it moved to the renovated "Semaphore Tower", within HMNB Portsmouth.