A microwave spark plug for injecting microwave energy into a combustion chamber of an engine including an elongated housing, including an elongated chamber forming a hollow conductor in an interior of the housing, and including a microwave window arranged at a first end of the chamber in the housing, wherein the microwave window closes the hollow conductor relative to the combustion chamber, wherein the hollow conductor includes a connection element for a high frequency feed conductor at a second end arranged opposite to the microwave window, wherein the connection element includes a high frequency inlet cross section geometry which differs from a high frequency outlet cross section geometry at the microwave window. The microwave sparkplug is configured to be threaded into typical boreholes for sparkplugs and facilitates safe injection of microwave energy into a combustion chamber of an internal combustion engine.