The 1955 season had been dramatically curtailed in the aftermath of the catastrophic Le Mans disaster in June, in which a Mercedes and other machinery caused the deaths of more than eighty spectators. In the wake of that tragedy the French Grand Prix was cancelled, and the German, Swiss, and Spanish Grands Prix were subsequently withdrawn from the calendar as well. Despite the reduced programme, the championship remained mathematically open after the British Grand Prix, but the cancellations ultimately meant Juan Manuel Fangio clinched the World Championship before the Italian race, securing the title for the third time overall and the second time in succession.
The Autodromo Nazionale di Monza near Milan had been extensively rebuilt for 1955. The circuit was resurfaced, given new pit facilities and safety infrastructure, and a new concrete banking was constructed over the site of the original, slightly banked loop. The combined road-and-banking circuit, measuring approximately 10 kilometres (6.214 miles), was used for the first time since 1933. The Curva Sud had also been redesigned, replacing two right-hand corners with a single sweeping right-hander known as the Parabolica, which included a run-off area.
Mercedes brought four W196 cars to Monza. Fangio and Stirling Moss drove the streamlined, closed-wheel versions of the W196, while Karl Kling and Piero Taruffi drove open-wheel variants of the same car. The appearance of the streamlined W196 at Monza was the fourth and final time that configuration raced at a World Championship round. The race also proved to be the third and last occasion in Formula One history that a championship race was won by a closed-wheel car.
The race produced a Mercedes 1–2 finish. It was the last Grand Prix victory for Mercedes-Benz as an engine manufacturer until David Coulthard won the 1997 Australian Grand Prix, and the last as a constructor until Nico Rosberg won the 2012 Chinese Grand Prix. The last 1–2 finish for Mercedes as an engine manufacturer came at the 1997 European Grand Prix with Mika Häkkinen and Coulthard; as a constructor, the next would not arrive until Lewis Hamilton and Rosberg at the 2014 Malaysian Grand Prix.
The race marked the final Formula One start for Nino Farina, the 1950 World Champion. Following the Italian Grand Prix, Mercedes-Benz announced its withdrawal from motorsport, ending a works programme that had dominated the 1954 and 1955 seasons with the W196 in Formula One and the 300 SLR in sports car racing.
The 1955 Italian Grand Prix occupies a unique place in motorsport history: it closed the most successful season of the W196's brief career, confirmed Fangio as champion for the third time, and served as the curtain call for one of the most technically advanced racing programmes the sport had yet seen. Mercedes-Benz's withdrawal, coming in the same year as Le Mans, reshaped the competitive landscape of Formula One for years to come.