A wood gas generator is a gasification unit which converts timber or charcoal into wood gas, a producer gas consisting of atmospheric nitrogen, carbon monoxide, hydrogen, traces of methane, and other gases, which – after cooling and filtering – can then be used to power an internal combustion engine or for other purposes. Historically wood gas generators were often mounted on vehicles, but present studies and developments concentrate mostly on stationary plants.

During the late 19th century internal combustion engines were commonly fueled by town gas, and during the early 20th century many stationary engines switched to using producer gas created from coke which was substantially cheaper than town gas which was based on the distillation (pyrolysis) of more expensive coal.

During World War II, gasoline was rationed and in short supply. Due to the lack of gasoline from petroleum, older people recalled how to build gasifiers for both wood and coal, and how to convert internal combustion engines to run on gaseous fuel, and wood gas generators were in active production. In Great Britain, France, the United States and Germany, large numbers of such generators were constructed or improvised to convert wood and coal into fuel for vehicles. Commercial generators were in production before and after the war for use in special circumstances or in distressed economies. Some World War II era wood gas generators were of the "Imbert" downdraft type, designed around 1920 by French inventor Georges Imbert.

Germany produced Gazogene units for vehicles including cars, trucks, artillery tractors and even tanks, to preserve the limited supplies of fuel. Even in non-combatant countries, such as Sweden, Brazil or Spain, gasogene was popular, as oil became hard to obtain. In Brazil, a racer named Chico Landi won at São Paulo's Interlagos circuit in 1944, driving a wood gas-powered Alfa Romeo.

When oil prices rose there was renewed interest in wood gas generators. The US Federal Emergency Management Agency (FEMA) published a book in March 1989 describing how to build a gas generator in an emergency when oil was not available. It described a design called the "stratified downdraft gasifier" which solves several drawbacks of earlier types.

The European Union sponsored a wood gas project in Güssing, Austria, starting in 2005. This project was an electric power plant with a wood gas generator and a gas engine to convert the wood gas into 2 MW electric power and 4.5 MW heat. There was also an experimental device to use the Fischer–Tropsch process to convert wood gas to a diesel-like fuel. By October 2005, it was possible to convert 5 kg of wood into 1 litre of fuel.

The Democratic People's Republic of Korea (North Korea) is also known to have trucks that run off of wood gas generators. The trucks are common outside of Pyongyang and are in rural villages and smaller towns. These trucks are utilized due to sanctions placed on North Korea regarding imports of oil and gas.

There is a rich literature on gas-works, town-gas, gas-generation, wood-gas, and producer gas, that is now in the public domain due to its age.