Rendering of the FF(X) frigate, based on the Legend-class cutter
Class overview
Builders	Huntington Ingalls Industries
Operators	United States Navy (projected)
Preceded by	Constellation class
General characteristics
Type	Frigate
Armament	Flight I 1 × BAE Systems Mk 110 57 mm gun 2 × 30 mm guns 1 × 21-cell Mk 49 RIM-116 Rolling Airframe Missile launcher Up to 16 × Naval Strike Missile launchers

FF(X) is the designation for a class of frigates intended for the United States Navy based on the National Security Cutter (NSC) or Legend-class cutter in service with the United States Coast Guard. The program was announced on December 19, 2025, and the ships will be built by Huntington Ingalls Industries.^[1]

On November 25, 2025, Secretary of the Navy John C. Phelan announced the cancellation of the Constellation-class frigate program beyond the first two hulls, citing the need to build ships at a faster rate.^[2]

The FF(X) program was announced on December 19, 2025, in social media posts by Phelan and Chief of Naval Operations Admiral Daryl Caudle.^[1] The program's objective is to have the first ship in the water by 2028.^[3]

Changes from the original NSC design include the construction of a platform above the stern boat deck for modular containerized payloads and unmanned systems.^[3] In the FF(X) renderings, a "shelf" was added to the bottom front end of the superstructure, presumably a space for future upgrades such as vertical launching systems (VLS), laser-based directed energy weapons or some other close-in weapon systems.^[4]

The initial flight of the class will be equipped with a Mk 110 57 mm gun, two 30 mm guns, a Mk 49 launcher for 21 RIM-116 Rolling Airframe Missiles for point defense and up to 16 RGM-184A NSM anti-ship missiles, but it will not feature an integrated VLS.^[5] Flight I ships will also lack anti-submarine warfare (ASW) equipment, though this capability may be added in the future.^[1]

The FF(X) is similar to HI Industries' 2012 "Patrol Frigate" proposal, also based on the Legend-class hull, previously offered to the U.S. Navy as a replacement for the Littoral Combat Ship.^[4] However, there are notable differences between the respective conceptual renderings, including variations in the size of the main superstructure and the gun turret.^[4] Notably, the Patrol Frigate design incorporated a 12-cell Mk 56 VLS unit, a capability not included on Flight I ships of the FF(X). The Patrol Frigate concept also included an expanded sensor suite.^[4]