An injection nozzle for injecting media into a combustion chamber includes a nozzle body having a tip with spray holes and protruding into the combustion chamber, and a heat protection sleeve that surrounds and is positioned on a combustion chamber side of an end area of the nozzle body. The injection nozzle is inserted into an accommodating hole of a retaining part, whereby the end area of the nozzle body interacts with the accommodating hole, and whereby the sleeve is positioned there-between. The sleeve further has a first and second area which are located at an axial distance from each other and which have respective sealing surfaces that interact in a sealing manner with either (i) an annular seat surface extending in a radial plane, or (ii) a cone-shaped seat surface of the accommodating hole or of the nozzle body.