Liquefied petroleum gas or liquid petroleum gas, also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.

It is widely used alternative fuel. It has substantial reserves due to its dual origins from natural gas processing and crude oil refining. Liquefied Petrol Gas (LPG) powered passenger cars have about 10% lower tailpipe CO2 emission than comparable gasoline powered cars. When compared to a diesel car, there is no significant CO2 emission reduction per km driven; however, LPG powered vehicles do have substantially lower NOx emissions than diesel powered vehicles.

It is an inevitable by-product of the crude oil refining process and of natural gas processing. In natural gas processing, the natural gas is cleaned off heavy hydrocarbons such as propane and butane before distribution. About 60% of global LP Gas supply comes from natural gas processing (WLPGA, 2011). In crude oil refining, LPG is a by-product of the refining process. LPG is gaseous at room temperature and changes to a liquid when compressed at moderate pressure or chilled. The chemical composition of LPG can vary, but is usually made up of butane and propane with a 30-99% propane mix.