A combustor is a small component or area of a gas turbine, ramjet or pulsejet engine where combustion takes place. It is also known as a burner.

Combustor design requires that part of the airflow be almost stationary where the fuel is mixed and ignites. This area of the combustor is sometimes called a flame holder and allows a stable flame front to be established and maintained. In the case of scramjet engines the combustor flow may be supersonic but few practical scram-jets have flown and their details are not published yet.

There are two categories of combustors, annular and can. Can combustors look like cans and are mounted around the engine. They can be easily removed for maintenance and provide convenient plumbing for fuel. Annular combustors are more compact and embedded deep within the engine's casing. Jet engines usually have annual combustors.

In a gas turbine engine the combustor is always located in a divergent duct formed at the upstream end of the combustion chamber of the core engine and others may be located in the tailpipe were the afterburner combustion takes place or in the offtake of compressed air from the compressor where that air is needed for thrust.

Combusters in rocket engines operate outside of the main rocket chamber and will usually be handling pre-combustion of fuel and LOX so that the mixture burns completely in the rocket motor combustion chamber.