A writing implement that includes a barrel extending in a longitudinal direction; a writing cartridge provided at one front end with a tip and designed to be moved in the barrel in the longitudinal direction between a forward position in which the tip is extended and a retracted position in which the tip is retracted into the barrel; a push member movable in the longitudinal direction and in a radial direction relative to the barrel, connected to the cartridge in order to move the latter, that includes at least one control member extending through an opening in the side of the barrel in order to project radially outwards, and also including at least one locking member designed to cooperate with a complementary locking member of the barrel allowing the push member to be locked in the forward position of the cartridge.