Extreme ultraviolet light source systems may include a chamber including a condensing mirror and having an intermediate focus, by which extreme ultraviolet light reflected from the condensing mirror is emitted along a first optical path, a blocking plate that may be on the chamber so as to intersect the first optical path and may include an opening through which the extreme ultraviolet light is emitted, a transparent cover on the blocking plate so as to cover the opening, a nozzle that may be between the chamber and the blocking plate so that an end portion faces the intermediate focus and may spray a first gas in a direction intersecting the first optical path, and an exhaust pipe between the chamber and the blocking plate so as to face the end portion of the nozzle.