The 1938 Grand Prix season was the sixth AIACR European Championship season. It saw the introduction of new rules that limited engine size to 3 liter, and added about 100 kg weight, thus some less competitive cars automatically complied to the new rules. The Mercedes-Benz W125 and Auto Union C with their large engines in low weight chassis had to be retired, and Mercedes-Benz W154 and Auto Union D appeared during the season.