Landing platform helicopter (LPH) is a term used by some navies to denote a type of amphibious warfare ship designed primarily to operate as a launch and recovery platform for helicopters and other VTOL aircraft. As such, they are considered a type of helicopter carrier.
Under the NATO Standardization Agreement (STANAG) document for reporting vessels, LPH is a short form designator used for "Amphibious Assault Ship, Helicopter" defined as a "large helicopter carrier" for carrying and deploying around 1,800 assault troops using its own aircraft, but for which use of landing craft is "not a principal function". For ships of this hull classification in the Royal Navy, LPH is a direct acronym for "Landing Platform Helicopter", while the United States Navy referred to its vessels within this classification as "amphibious assault ships". The etymology is L for amphibious, P for transport, and H for helicopter. Regardless of the terminology, all vessels classified as an LPH possess essentially similar capabilities.
The Royal Navy also used the term "Commando Carrier", which it applied to aircraft carriers converted to helicopter only operations. Prior to selling the vessel to the Brazilian Navy in 2018, the RN operated HMS Ocean as an LPH. Following the British government's decision to withdraw its Harrier aircraft at the end of 2010, the former light fleet carrier HMS Illustrious also performed this role until decommissioning in 2014.
The LPH classification was used by the U.S. Navy for the amphibious assault ships of the Iwo Jima class, a converted Casablanca-class escort carrier and three converted Essex-class aircraft carriers. No ships of this classification are currently in active service with the U.S. Navy, having been replaced with multi-purpose ships classified under NATO naming conventions as landing helicopter dock or landing helicopter assault ships.
Royal Navy "Commando Carriers and "Amphibious Helicopter Carriers"