The 1926 Grand Prix season was the second AIACR World Manufacturers' Championship season and the first running to new 1.5-litre regulations. The championship was won by Bugatti and its Type 35 was the dominant car of the year.
The schedule was increased from four to five championship races. The Belgian round was dropped but the British Grand Prix and San Sebastián Grand Prix were added. Many races had promising entry lists, but when a number of cars did not arrive, it led to farcical races with just a handful of starters and only a couple of finishers.
The leading French teams of Bugatti, Delage and Peugeot arrived for the Targa Florio as, once again, the major Italian teams did not enter. The race was marred by the death of two-time winner Giulio Masetti, crashing his privateer Delage on the first lap. Once again it was the small, nimble Bugatti of Bartolomeo Costantini that held off the rest of the pack. When the works Delage team was withdrawn following Masetti's death, it left Costantini led his team to a 1-2-3 victory.
The opening race of the championship was the Indianapolis 500. Frank Lockhart was a young rookie who substituted in to race for an ill Pete Kreis. Starting from back in the pack he soon joined the leaders and took the front on lap 60. On lap 71, rain forced a stop to the race for over an hour. Upon the restart, Lockhart built up his lead again, so at the 400-mile mark he had a 2-lap lead over the field. At that point rain returned, and he became the first rookie winner since 1914, in the rain-shortened race.
The European rounds of the championship were plagued by entry withdrawals of the works teams, leaving just a handful of starters to contest the races. The most embarrassing was the premier French Grand Prix where only the three Bugatti works cars started, and Jules Goux won, being the only classified finisher. The Delages were fast but poorly designed with the exhaust system placed right beside the drivers’ legs causing burns and exhaustion so that the team lost race-winning opportunities from numerable pit-stops to rest and recover. They did win the inaugural British Grand Prix as Bugatti did not enter and the new Talbots were still too under-developed. In the end, by virtue of being the only team to run the mandatory three races, Bugatti won the second Constructor's Championship.
Outside the championship, Formula Libre races (literally, open formula) were very popular across France and Italy and a number were staged with large fields of local drivers. Germany held its first Grand Prix, won by the young Rudolf Caracciola in difficult wet conditions that caused several serious accidents.