A laser spark plug for an internal combustion engine, in particular for a gas engine, includes a laser crystal integrated into the laser spark plug and a combustion chamber optical unit. Laser light pulses issuing from the laser crystal can be coupled by way of the combustion chamber optical unit into a combustion chamber of the internal combustion engine. An optical laser light sensor is integrated into the laser spark plug, and the combustion chamber optical unit is provided with a preferably curved reflection surface which faces towards the laser light sensor and has a reflective mirroring. At least a part of a laser light reflected at the reflection surface during the duration of a laser light pulse can be detected by the laser light sensor.