Louis Rosier was born on 5 November 1905 in Chapdes-Beaufort in the Auvergne region. He apprenticed as a mechanic, operated a garage in Clermont-Ferrand, and began competing in motorcycle hillclimbs in 1927 before transitioning to four-wheeled racing. During World War II he served in the French Resistance, using his garage as a base for Resistance activities; his wife and daughter were captured by German forces and held in Germany before being freed in 1945. He resumed racing in 1946.
Post-war, Rosier funded his racing through a prominent Renault dealership in Clermont-Ferrand, one of the largest in the country. He established Écurie Rosier around 1948, initially centred on a Talbot-Lago T26C, and competed as a privateer against factory-supported teams throughout his career. His four consecutive French national championships from 1949 to 1952 measured his domestic dominance.
Before the Formula One World Championship began, Rosier recorded significant non-championship results including the 1949 Belgian Grand Prix at Spa-Francorchamps in a Talbot-Lago T26C, a victory he achieved ahead of factory-backed entries. He also won the Dutch Grand Prix at Zandvoort in 1950 (non-championship) and the Grand Prix d'Albi in 1947, 1950, and 1952, among other events.
Rosier's most celebrated result came at the 1950 24 Hours of Le Mans. Co-driving a Talbot-Lago T26 GS with his son Jean-Louis, who completed only a handful of laps, Rosier drove for close to 23 hours himself to take overall victory. The run was complicated by an owl striking the windscreen during the night, shattering the car's glazing and injuring his eye. The win represented Talbot-Lago's last major success at the event and demonstrated the endurance tactics — long stints, fuel conservation, mechanical sympathy — that characterised Rosier's approach to racing.
Under the Écurie Rosier banner, Rosier entered the World Championship at the 1950 Monaco Grand Prix and continued through to 1956, primarily driving Talbot-Lago, Ferrari, and Maserati machinery. His 1950 season was the strongest, yielding third places at the Swiss and Belgian Grands Prix, the latter achieved by running non-stop while rivals made pit stops, and a fourth-place finish in the French Grand Prix at Reims. He placed fourth in the 1950 drivers' standings.
In 1951 Rosier again fielded a Talbot-Lago, with Henri Louveau and Louis Chiron driving for the team in those early seasons. Chiron raced in most rounds of 1951, recording a string of retirements. Rosier himself finished fourth in Belgium in 1951.
The team's 1954 season was its best in terms of guest driver results. Maurice Trintignant drove for the team and finished fourth in Argentina. Robert Manzon delivered the team's sole World Championship podium by finishing third at the French Grand Prix at Reims. Rosier also entered the new Maserati 250F at the 1954 Spanish Grand Prix and finished seventh.
From 1955 Rosier raced only a single car for himself. The 1956 German Grand Prix, where he finished fifth, proved to be the team's final World Championship entry. On 7 October 1956, Rosier crashed his Ferrari 750 Monza at the Coupe du Salon at Montlhéry in wet conditions on the first lap. He died from his injuries on 29 October 1956 in Neuilly-sur-Seine, aged 50.
Beyond Formula One, Rosier entered Le Mans nine times between 1938 and 1956 under various banners including Écurie Rosier, achieving his single outright victory in 1950. A 1951 Le Mans entry shared with Juan Manuel Fangio retired with an oil tank failure. He also raced at Le Mans with co-drivers including Maurice Trintignant and Robert Manzon without further classified finishes. His final sports car win came at the 1956 Paris 1000 km at Montlhéry, shared with Jean Behra in a Maserati 300S, months before his fatal accident at the same circuit.
Rosier had been instrumental in promoting and helping fund the construction of the Circuit de Charade near Clermont-Ferrand, a challenging track built on volcanic mountain roads around the Puy de Gravenoire. The circuit opened on 27 July 1958 — nearly two years after his death — and was named the Circuit de Charade Louis Rosier in his honour. It later hosted the French Grand Prix and French Motorcycle Grand Prix on multiple occasions, and the Virage Louis Rosier corner within the circuit preserves his name to this day.