The 1939 championship ran under the same regulations introduced in 1938: a maximum of 3 litres for supercharged engines and 4.5 litres for unsupercharged, with an increased minimum car weight. The Italian Grand Prix had originally been planned as a fifth round but was cancelled well before the season due to construction work at Monza, reducing the championship to four events. The season proceeded against the backdrop of increasing European military tension; Germany's annexation of Czechoslovakia in March 1939 had made war appear increasingly likely, and the final Swiss Grand Prix at Bremgarten was run on 20 August 1939, eleven days before Germany invaded Poland.
The season produced an unusual dispute about the rightful champion, arising from the existence of two different scoring systems and the failure of the AIACR to rule definitively before the war ended organised international racing.
In the first two championship events, both Hermann Lang and Hermann Paul Müller each won once while the other failed to complete 75% of the race distance — leaving both men's points tallies dependent on the scoring method used. At the German Grand Prix, Lang retired early while Müller finished second behind Caracciola. This left Müller ahead in both scoring systems with one round remaining.
At the Swiss Grand Prix, Lang won ahead of Caracciola and Richard Seaman, with Müller finishing fourth. Under the French maximum-points system — similar to modern championship formats — Lang's win was enough to overhaul Müller and claim the title. Under the older minimum-points system, which essentially counted positions, Müller's fourth place was sufficient to maintain his lead.
Contemporary magazines, publishing live championship standings, showed Müller leading after the Swiss round under the older system, while Lang had the title under the French points method. The AIACR did not resolve the ambiguity before the war intervened. The president of the NSKK — Nazi Germany's highest motorsport authority — subsequently declared Lang the champion, a decision that was accepted by the German and international press despite the formal absence of an AIACR ruling. Modern motorsport historians generally acknowledge Lang as the dominant driver of 1939, given his two victories and overall pace through the season, though Müller's counter-claim based on the older scoring criteria is documented.
Lang had emerged through the Mercedes-Benz ranks as a former factory mechanic and reserve driver, gradually gaining race duties through 1936 and 1937. By 1939 he was the team's leading performer, faster over the course of the season than the experienced Caracciola. His rise represented a significant shift in the internal hierarchy of the dominant team of the era.
Richard Seaman, the English privateer who had risen through the voiturette ranks to earn a Mercedes works drive, finished third at the Swiss Grand Prix — his final race result. He had been killed in a fire at the Belgian Grand Prix in June 1939, the only non-championship race of significance during the season.
Auto Union, still rebuilding after the deaths of Rosemeyer in 1938 and Ernst von Delius in 1937, continued to campaign the Type D but without the same frontrunning presence as in earlier seasons.
The 1939 European Championship was the last in the pre-war series that had run since 1931 and been reinstated in 1935. The combination of German engineering, government financing, and the particular talents of drivers like Caracciola, Lang, and the earlier Rosemeyer had shaped six seasons of comprehensive German dominance in the sport's premier category. When international grand prix racing resumed after the war, the sport's organisational structure, technical regulations, and competitive landscape had all fundamentally changed; the 1950 World Championship of Drivers represented a new beginning rather than a continuation. The 1939 championship, and the era it closed, remained a reference point for the extreme capabilities attained under the 750 kg and subsequent 3-litre supercharged formula.