The French Armaments Agency (DGA) announced on September 12, 2025, it had awarded ArianeGroup the contract to design and build the new M51.4 strategic ballistic missile, marking the start of work on the fourth version of France’s sea-based nuclear deterrent.
The contract itself was signed on August 28, 2025, and covers both the development and production phases of the missile.
The M51.4 will equip the current Le Triomphant-class nuclear-powered ballistic missile submarines (SSBN) as well as the future third-generation SSBN (SNLE-3G) now in production at Naval Group. According to the DGA, the missile’s enhanced range, accuracy, and defense-penetration capabilities will help maintain the credibility of France’s oceanic deterrent against evolving threats.
“This contract coincides with the entry into service of the M51.3, the missile’s latest version, and the acceleration in production at ArianeGroup in line with the agreed schedule,” said Vincent Pery, Director of Defence Programs at ArianeGroup. “On behalf of ArianeGroup and all the teams, I would like to thank DGA for its renewed confidence in our highly strategic expertise and capabilities, which are vital to France’s Strategic Oceanic Force.”
An incremental upgrade path
The M51 program is built around successive versions, each designed to meet evolving operational needs and incorporate new technologies. The M51 entered service in 2010 on the Triomphant-class, replacing the older M45.
The M51.2 introduced the TNO new-generation warhead, while the M51.3, developed from 2014 and successfully test-launched in 2020, 2021, and 2023, is expected to enter service in 2025. It features an improved third stage for extended range and greater ability to penetrate missile defenses.
The newly contracted M51.4 will succeed the M51.3 in the 2030s, with a development budget of €7.5 billion. France describes its improvements as crucial for keeping pace with global advances in missile defense.
Industrial and strategic role
ArianeGroup, a joint venture between Airbus and Safran, has been the industrial prime contractor for the M51 since 2000, responsible for design, production, maintenance, and end-of-life dismantling. The company says the M51.4 program will sustain activity across its own facilities and those of hundreds of partner suppliers for years to come, while introducing new methods and technologies to meet ambitious technical and cost targets.
The DGA noted that regular non-nuclear test firings from submarines and the Landes missile range are part of the program to demonstrate and maintain capability.
France currently operates four Triomphant-class submarines, each capable of carrying up to 16 M51 missiles. These boats are being refitted to deploy the latest versions of the missile. In parallel, Naval Group is building the first SNLE-3G submarine, with the construction launched in March 2024 in Cherbourg, which will eventually replace the Triomphant-class.
A broader modernization
France maintains fewer than 300 nuclear warheads, relying on both its sea-based SSBN fleet and its airborne component. Alongside the M51.4, development continues on the ASN4G, a fourth-generation air-launched hypersonic missile intended to replace the ASMPA cruise missile by 2035.
The DGA stressed that incremental improvements to the M51 are not only about operational effectiveness but also about preserving France’s industrial base. By phasing upgrades, the program ensures the long-term skills and capacity needed for missile development remain within the French defense industry.
