Alfa Romeo's earlier P2 had been a success, but by the early 1930s the design was aging. Jano returned to the drawing board to produce a car that could sustain competitiveness over longer race distances, taking lessons from the P2's known limitations. The result was the P3, which Alfa Romeo designated as the second monoposto after the Tipo A of 1931, though the P3 is considered the first true single-seater because the Tipo A was in effect a pair of side-by-side monocoques joined together.
The P3 was powered by a supercharged straight-eight cylinder engine, and despite using a cast iron engine block it weighed just over 680 kg — unusually light for a Grand Prix car of the period. Engine displacement grew during the car's competitive life: the original 2.65-litre unit was enlarged to 2.9 litres for 1934 when new regulations mandated larger bodywork, and to 3.2 litres for select races in 1935.
The P3 was introduced mid-season at the 1932 European Grand Prix season in June, winning its debut race driven by Tazio Nuvolari. It went on to win six races in 1932, with victories shared between Nuvolari and Rudolf Caracciola, including all three of the major Grands Prix — the Italian, French, and German.
The 1933 season was complicated by financial difficulties at Alfa Corse. The factory locked the P3s away initially and had Enzo Ferrari's breakaway Scuderia Ferrari team run the older Alfa Monzas instead. After protracted negotiations, the P3 was handed to Scuderia Ferrari in August; the cars then won six of the final eleven events of the season, including the final two major Grands Prix in Italy and Spain.
In 1934 new bodywork regulations prompted the engine enlargement to 2.9 litres. Louis Chiron won the French Grand Prix at Montlhery for the P3, but the arrival of the German Silver Arrows — the Mercedes W25 and Auto Union — dominated the European Championship's other rounds. Despite this, P3s won 18 of 35 Grands Prix contested across Europe that year, illustrating how uneven the competitive landscape was between the championship rounds and the broader calendar.
By 1935 the P3 was outpowered in the six European Championship rounds against the superior German machinery. Yet the car produced one of the most celebrated victories in pre-war racing: the 1935 German Grand Prix at the Nürburgring, run in front of some 300,000 spectators and in the heartland of Mercedes and Auto Union. Nuvolari, driving a P3 bored to 3.2 litres, punctured a tyre while leading but recovered through the field. On the final lap, Manfred von Brauchitsch's Mercedes W25 — which had been leading — suffered a puncture, and Nuvolari swept past to win. The victory remains one of the most famous upsets in motorsport history. The P3 went on to win 16 of 39 Grands Prix contested in 1935.
The car continued to race with private entrants into 1936, with drivers including Raymond Sommer and others across European events.
The P3's designation as the first genuine single-seat Grand Prix racing car gives it a foundational place in motorsport history: the monoplace configuration it pioneered became the universal format for top-level Grand Prix and Formula One cars thereafter. Nuvolari's 1935 German Grand Prix win with the P3 — beating the technically superior Silver Arrows on their home circuit — became a defining story of courage and tactical racecraft in the sport's pre-war canon. The car also confirmed Vittorio Jano as one of the era's greatest racing car designers, a reputation built on the P2 and sustained across four seasons of P3 competition.
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