The company was founded as Josef und Franz Werndl and Company in 1864 as a rifle manufacturer, but became known as Steyr-Werke AG in 1924. The company began producing bicycles in 1894, and Steyr automobiles in 1915. The first Steyr cars (Type II) were heavy and well-built, if a little cumbersome; soon however they developed sports versions with an impressive list of international achievements. The small but luxurious 1.5-liter six Type XII of the late twenties won international motor press acclaim.
In 1934, Steyr merged with Austro-Daimler-Puch to form Steyr-Daimler-Puch. The range produced in these years mainly consisted of very modern designs, sporting partially or complete unit construction bodies in streamlined livery, from the 1.200 ccm Steyr 50 to the 2.3 liter 220 six.
During the World War II the Steyr-Daimler-Puch cartel used slave labour in the German concentration camps extensively, notably in the Mauthausen-Gusen camp complex at Gusen; the product range was entirely for military use, including the Raupenschlepper Ost with an air-cooled 3.5 liter V8 engine. After the war they built Diesel engined trucks and buses, small and heavy tractors and also resumed passenger car production. First Steyr assembled the FIAT 1100 E, then put their own engine in a FIAT 1400, renaming the car the "Steyr 2000". From 1957 till the early seventies they produced the tiny Puch 500 under license from FIAT, again with an engine of Austrian design. Most prominent, however, was their range of off-road cars, from the two-cylinder Haflinger and the heavy 4 x 4 or 6 x 6 Pinzgauer to the Mercedes-Puch G.
The conglomerate was broken up in 1990, with Steyr Tractor being sold to Case Corporation, Puch's motorcycle division going to Piaggio, Steyr Mannlicher producing weapons, and Steyr's automobile production combined with Magna as Magna Steyr.
The diesel engine division was spun off into STEYR Motorentechnik GmbH, which in 2001 became an independent company, renaming itself Steyr Motors GmbH.
SDP was the initial designer and manufacturer of the utility vehicles, the Haflinger, produced from 1959 to 1974, the Pinzgauer, produced from 1971 till 2000 and the Puch G produced from 1979 which is also known as Mercedes G-Class.
In 1998 the production of military vehicles was sold to an Austrian investor company which sold the company called Steyr-Daimler-Puch Spezialfahrzeug GmbH (SSF) in 2003 to the US-company General Dynamics.