The 1933 Grand Prix season was in an intermediate year, as it would be the last season for the current AIACR regulations before a new weight-formula was introduced in 1934. As such, the European Championship was not held and the manufacturers held back on further developments of their existing models. Alfa Romeo, following an Italian government financial bailout and like Mercedes-Benz the previous year, had shut down its Alfa Corse works team. Scuderia Ferrari, their regular customer team took up the role of racing Alfa Romeos and a number of ex-works drivers moved across to join their ranks. They were not allowed, however, to buy the impressive Tipo B that had been so dominant in the previous season.

The season had some exceptional races and fell into two distinct halves. Initially it was Tazio Nuvolari, driving for the Scuderia Ferrari, that dominated. However, after winning the Tunisian Grand Prix he was plagued by mechanical problems and retiring out of race-winning positions. A thrilling race-long battle with Achille Varzi at the Monaco Grand Prix was decided on the second-to-last lap when the engine on Nuvolari's Alfa broke. He was untouchable at a wet Nürburgring but retired in the French Grand Prix - a race won by the veteran Giuseppe Campari in the new Maserati model. In the middle of these was one of the most controversial pre-war races yet held – the Tripoli Grand Prix. It was held in conjunction with a multi-million national lottery to win tickets for each of the drivers. In the race, it again became a Varzi-Nuvolari duel, decided at the last corner when Varzi outbraked Nuvolari to win by a fifth of a second.

The frustration came to a head after a third axle-failure and Nuvolari, with close friend Borzacchini, walked out of Ferrari straight across to Maserati. Luigi Fagioli, lead-driver of the Maserati works-team, was furious that his great rival had been approached and in response took the vacant position at Ferrari, soon to be joined by Campari. Nuvolari won successive races with the Maserati at Spa, Montenero and Nice. Alfa Romeo, now concerned that they were losing their pre-eminence, released their Tipo B cars to Ferrari. Fagioli won on the car's return, at the Coppa Acerbo after Nuvolari had a mechanical retirement.

In the Italian Grand Prix, Fagioli benefited from Nuvolari's misfortune after he got a puncture while leading with two laps remaining. The Monza GP was run in the afternoon, held as three heats to qualify for the final. In the second heat, Campari and Borzacchini both crashed on the oval banking and were killed. Then, in the final, Stanisław Czaykowski was also killed at almost the same place. Subsequently, known as the "Black Day of Monza", it was a further tragic weekend in a deadly year of motorsport.

The last major race of the year was the Spanish Grand Prix that finally saw the debut of Bugatti's new Type 59, the model for the new formula. A mid-race downpour saw Nuvolari aquaplane off the track and crash, thereby giving Chiron his third victory of the season and Ferrari its third 1-2 finish.

This year the AIACR elevated the Monaco Grand Prix to the exclusive rank of Grand Épreuve, hitherto only held by the other six national races of their member bodies, alongside the Indianapolis 500 for the US and the Tourist Trophy for Great Britain. These held special scheduling privileges that the CSI would set the racing calendar around, and other international events could not be held on the same day opposite those races. They also attempted, unsuccessfully, to tighten up on the usage of “Grand Prix” to limit it to the premier event of each of the affiliated associations.

A pink background indicates the race was run for Sports Cars or Touring Cars this year, while a grey background indicates the race was not held this year. Sources:

Multiple classes are mentioned when they were divided and run to different race lengths.