The A.L.F.A 24 HP came on the market in 1910. This was the first automobile created by A.L.F.A (later Alfa Romeo). Giuseppe Merosi was the man behind engineering. The car was used for the first time in car racing in the 1911 Targa Florio. This was first commercial success for the company and the timeline of the HP series tells that the car was continuously developed onwards. The 24HP had a 4,082 cc (249.1 cu in) straight-4 sidevalve engine, which produced 42 bhp (31 kW) with 2200 rpm and gave top speed of over 100 kilometres per hour (62 mph). Until 1913 approximately 200 A.L.F.A 24 HPs were built.

The engine designation consisting of a number as well as "HP" came from the then usual designation of tax schedules. The 24HP became the starting point of a whole series of vehicles, which were built until 1921.