The M51.3 submarine-launched ballistic missile developed by Franco-German defense firm ArianeGroup has entered service with France’s Strategic Oceanic Force (FOST).
FOST, a branch of the French Navy responsible for the country’s sea-based nuclear deterrent, will deploy the M51.3 aboard its four Le Triomphant-class nuclear ballistic missile submarines (SSBNs).
The M51.3 is the third version of the M51, a fifth-generation strategic ballistic missile first fielded in 2010, and will gradually replace the M51.1 and M51.2 variants.
Its development spanned 10 years, was completed on schedule, and stayed within the initial budget. The missile’s entry into service follows the French defense procurement agency (DGA) awarding ArianeGroup a new contract to develop the M51.4 in August 2025.
Vincent Pery, Director of Defence Programs at ArianeGroup, expressed thanks to the DGA and French authorities “for their confidence in ArianeGroup’s expertise and role as prime contractor” for the M51 program’s entire lifecycle.
“In today’s evolving geopolitical context, deployment of the M51.3 helps ensure the continued credibility of France’s oceanic nuclear deterrent,” he added.
M51.3 Development
The latest M51 variant completed qualification tests in southwestern France in November 2023.
In the next two years, it underwent more tests that validated its overall performance and compliance with nuclear safety standards at the Île Longue base and aboard SSBNs.
Assessments were concluded in September 2025.
Its operational commissioning this month “embodies a major ambition of the 2024-2030 Military Programming Law: to accelerate the modernization of our capabilities and ensure the long-term credibility of our deterrence, the sovereign pillar of our security,” French Armed Forces Minister Catherine Vautrin wrote in a social media post.
M51 Missiles
Missiles under the M51 series measure about 12 meters (39 feet) long, weigh over 50 metric tons (110,000 pounds), and use a solid-propellant three-stage propulsion system.
Each of the FOST-operated SSBNs carries 16 M51 missiles. When launched from a submerged submarine, the missile travels beyond 2,000 kilometers (1,240 miles) into space before re-entering the atmosphere at around Mach 20.
