The French Ministry of the Armed Forces announced that the third version of the M51 submarine-launched ballistic missile (SLBM) known as “M51.3” entered operational service on 24 October 2025.
The M51.3 will be deployed aboard the Le Triomphant-class nuclear-powered ballistic missile submarines (SSBN) of the French Navy.
Developed by ArianeGroup (acting as the prime contractor) under the supervision of the French defence procurement and technology agency, DGA, the M51.3 missile offers improved range, accuracy, and penetration capabilities. According to French authorities, the new SLBM reinforces the credibility of the oceanic component of France’s nuclear deterrent in the face of evolving adversary missile defenses. It carries the new oceanic nuclear warhead (TNO-2), designed and guaranteed through the Simulation program of the French Atomic Energy Commission (CEA).
“This operational deployment marks the culmination of the M51.3 and TNO-2 programs, respectively conducted and launched by the DGA in 2014 and by the CEA in 2013. The execution of these programs, anchored in the long-term framework of military planning law, ensures the continuity of our capabilities for this strategic mission” the French Ministry of the Armed Forces said in a release.
The three-stage engine of the M51 is so good that it served as base to develop the solid propellant boosters of the European Ariane 5 space rocket. Open source data indicates an M51 weight of 52,000 kg, a length of 12.0 m and a diameter of 2.3 m. M51 operational range is reported to be 8,000 to 10,000 km with a speed of Mach 25.
The first test launch of an M51 ballistic missile was successfully carried out at Centre d’essais de lancement de missiles (CELM) in Biscarosse, France, on November 9, 2006. The sixth missile test carried out on May 5, 2013, ended in failure. The latest M51 tests in September 2015, July 2016, June 2020 and April 2021 and April 2023 were all successful.
The French military announced it successfully test-fired a new submarine-launched ballistic missile (SLBM) on 18 November 2023, from a land-based test facility. This was first ever launch of the M51.3 SLBM.
In September 2025, the French DGA awarded ArianeGroup a contract to design and produce the fourth version of the M51 submarine launched ballistic missile (SLBM) known as “M51.4”. The M51.4’s enhanced range, precision and penetration capabilities will reinforce the credibility of France’s oceanic nuclear deterrent in response to evolving threats.
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