A by-pass turbojet including a thrust reverser is disclosed. The thrust reverse includes a deflector device which deflects all or part of the primary stream gas in such a manner that the deflected primary stream gas encounters the secondary stream, thereby reducing the injection speed of the secondary stream in an aft direction, and thus generating the thrust-reversal effect. The secondary stream escapes from the aft end of the nacelle. In the thrust-reversal position, the deflector device is inscribed radially substantially within the section of the primary nozzle cowl at the aft end of the nacelle. Such a thrust reverser is particularly simple in design, inexpensive, and makes it possible to avoid having moving parts present on the outside portion of the nacelle, thus simplifying the design of the turbojet.