The Horizon class (French: Classe Horizon; Italian: Classe Orizzonte) is a class of air-defence destroyers in service with the French and Italian navies. They are designated as destroyers by the Italians^[7] and using NATO classification but are referred to as "frigates" by the French. The programme started as the Common New Generation Frigate (CNGF), a three-nation collaboration between France, the United Kingdom, and Italy to develop a new generation of air-defence warships.^[8] Differing national requirements, workshare disagreements and delays led to the UK withdrawing from the project in 1999 to develop the Type 45 destroyer.^[9]

The FREMM multipurpose frigate were built using the same company structure as the Horizon project.

France, Italy, and the UK issued a joint requirement in 1992 after the failure of the NATO Frigate Replacement for the 90s (NFR-90) project. In July 1993, the three countries signed a Memorandum of Understanding for a Common New Generation Frigate (CNGF).^[10] The ships were to be armed with the Principal Anti Air Missile System (PAAMS). The UK intended to purchase twelve ships to replace its Type 42 destroyers. France was to purchase four to replace its Suffren class, and Italy would purchase six to replace its Andrea Doria and Audace-class ships.^[11]

Problems emerged almost immediately. The primary problem was that of differing requirements: France wanted anti-aircraft warfare (AAW) escorts for its aircraft carriers, but only a limited range was necessary due to the self-defence capability of the French Charles de Gaulle. Italy too required only close-range capabilities, as in its home waters of the Mediterranean Sea the ships would operate under Italian Air Force cover or escorts for its aircraft carrier Cavour. The Royal Navy, however, required more capable ships which could throw a large defensive "bubble" over a fleet operating in hostile areas.^[12] The compromise that largely solved this problem was the adoption of a standard radar interface, which allowed France and Italy to install the EMPAR multi-function passive electronically scanned array radar and the UK to install the more capable SAMPSON active electronically scanned array radar—the SAMPSON radar has a higher data rate and an adaptive beam that allows a greater ability to track multiple targets, long-range detection of low-RCS targets, a lower false-alarm rate, and overall higher tracking accuracy.^[13]

In March 1996, it was agreed that the PAAMS office would be based in Paris, and the Project Horizon project office would be based in London. The latter was to be responsible for the design of the ship, its command and control, and secondary weapons systems. Britain also agreed to contribute £100m in recognition of the development work already completed by Italy and France on PAAMS.^[11] Construction would be carried out by DCN (France), GEC-Marconi (UK), and Orizzonte (Italy).^[11]

• Arleigh Burke-class destroyer
• Kolkata-class destroyer
• Atago-class destroyer
• Sejong the Great-class destroyer
• Type 052D destroyer