Lang was born in Cannstatt, near Stuttgart in Baden-Württemberg. When his father died, he was obliged to leave school at fourteen to help support his family, finding work as a motorcycle mechanic. In his spare time he bought a used motorcycle and began amateur racing, winning the first event he entered. He progressed to sidecar racing and by the age of twenty-two had won the German sidecar mountain race championship.
His talent and mechanical knowledge eventually brought him to the attention of the Mercedes factory, where he was hired as part of the Grand Prix motor racing team. His first major responsibility was as head mechanic for the Mercedes-Benz W25A, assigned to look after the car driven by the Italian star Luigi Fagioli. This role gave Lang an intimate understanding of the machinery that would later prove a significant competitive advantage.
After Fagioli enjoyed a successful season that included wins at the Italian and Spanish Grands Prix, Lang was given the opportunity to drive. He quickly demonstrated that his abilities extended far beyond mechanical preparation. He proved especially fast on high-speed circuits, and in 1937 he won the Tripoli Grand Prix at the Mellaha Lake circuit in Libya — then considered the fastest racetrack in the world. He would go on to win the Tripoli Grand Prix three consecutive times.
Also in 1937, Lang won at the AVUS circuit in Germany, another power circuit that suited his driving style. In 1938 he added further victories, including the prestigious Coppa Ciano at Livorno, consolidating his reputation as a genuine frontrunner rather than a fill-in driver.
The 1939 season was the peak of Lang's pre-war career. He won five of the eight Grand Prix races he started, taking victories at the Belgian Grand Prix, the Pau Grand Prix in France, the Swiss Grand Prix, and a third successive Tripoli Grand Prix. He also won the Kahlenberg hillclimb in Austria. His mechanical background made him an unusually valuable driver to Mercedes chief designer Rudolf Uhlenhaut, as Lang could articulate technical feedback precisely enough to guide development of the cars to a higher standard than rivals were achieving.
Despite this dominance, Lang's season ended in controversy. The German motor racing authority awarded him the title of European Champion for 1939, but the season had been cut short by the outbreak of the Second World War. The official governing body, the AIACR in Paris, had not ratified the championship, and by the points standings at the last race attempted, competitor Hermann Paul Müller was actually leading. The 1939 European Championship title remains disputed.
Lang's position within the Mercedes team was complicated by class tensions that were never entirely resolved. The Silver Arrows squad was dominated by wealthy and aristocratic drivers who regarded the uneducated, working-class Lang as an outsider. Even as his results mounted, he was never fully accepted by his teammates and team hierarchy on equal social terms. His five victories in 1939 compelled a grudging acknowledgment of his ability, but the social barrier remained a persistent feature of his time at Mercedes.
The Second World War effectively eliminated Lang's best competitive years. He returned to racing in 1946 without a factory team, famously winning the first post-war race held in Germany at Ruhestein, driving a six-year-old BMW. By 1949 he was competing in sports car racing, and in 1951 he rejoined Mercedes for Formula Libre races in Argentina, finishing second and third at the Buenos Aires events in the pre-war W154.
In 1952, at the age of forty-three, Lang partnered Fritz Riess in a Mercedes-Benz 300SL to win the 24 Hours of Le Mans — a remarkable result for a driver of his age, more than a decade after his Grand Prix peak. That year's planned return alongside Rudolf Caracciola and Luigi Fagioli, two veterans of the pre-war era, was disrupted when both suffered career-ending crashes before the race.
In 1953, Lang drove for Maserati in two Formula One World Championship races, scoring a fifth-place finish at the Swiss Grand Prix. When Mercedes returned to Formula One in 1954 with the W196, Lang was given a chance at the German Grand Prix at the Nürburgring but struggled, spinning out after ten laps having qualified significantly slower than team leader Juan Manuel Fangio. He recognised that his competitive time had passed and retired from racing, returning to his position at the Mercedes factory.
Hermann Lang published his autobiography, Grand Prix Driver, in 1953, with a foreword by Mercedes team manager Alfred Neubauer; it was subsequently translated into English by Charles Meisl. His career demonstrated that mechanical talent and raw speed could overcome social disadvantage at the very highest level of the sport, even within a team environment that was far from welcoming. The five Grand Prix victories in 1939 and the 1952 Le Mans win separated by more than a decade represent a span of achievement that few drivers of his era could match.