Automatically orientable air diffuser according to the temperature of the discharge air, with limitation of travel, the diffuser being of the type of those which are installed embedded in the wall of the enclosure which is to be conditioned, the diffuser comprising: an outer casing; an inner body, assembled inside said casing with the possibility of pivoting with respect to two pivoting anchor points with the mentioned casing, located in diametrically opposite positions defining a horizontal axis of rotation; an articulated lever, pivoting with respect to its upper end in relation to a support integral with the mentioned casing through an arm, and which at the opposite end is attached to the mentioned inner body to pivotably drive said inner body and cause the change of position thereof; a spring acting directly on the articulated lever, forcing it to move backwards to a limit determined by an adjustable stop, thus taking the mentioned inner body towards the cold air discharge position, and a unit associated with a heat-expandable element, located in the direction of passage of the discharge air, which has a front portion which can push on the mentioned articulated lever, against the action of the spring, when the temperature of the discharge air rises and said heat-expandable element expands, to thus take the inner body to the hot air discharge position, the mentioned diffuser furthermore includes a stop element, that forms an effective stop with respect to the pivoting travel of the inner body when it is pushed by the expansion of the heat-expandable element through the mentioned articulated lever, the heat-expandable element is configured such that it has a perimetrically thickened portion determining a front portion with which it performs the push on the mentioned articulated lever and a rear portion, characterized in that the stop element, adopting the form of an angle bracket profile, is assembled in the mentioned casing by means of one of its branches with the possibility of adjustable positioning, for which purpose it includes a pivoting securing hole and a slit opening, formed with a certain inclination with respect to the longitudinal direction of the branch of the part, through which there passes a screw or the like for fixing the stop element in the chosen position, whereas the other branch of the angle bracket is projected behind the casing, and in that the rear portion, carrying a spring pressed thereon and supported at the opposite end in a bushing is configured such that it has a tubular portion sized to be coupled in a hole of a support element, such that when the heat-expandable element continues to expand due to the effect of the temperature of the discharge air after the inner body has reached the end of its travel, against the stop, said heat-expandable element can move backwards against the action of the spring, absorbing with the effect of this additional expansion. an outer casing; an inner body, assembled inside said casing with the possibility of pivoting with respect to two pivoting anchor points with the mentioned casing, located in diametrically opposite positions defining a horizontal axis of rotation; an articulated lever, pivoting with respect to its upper end in relation to a support integral with the mentioned casing through an arm, and which at the opposite end is attached to the mentioned inner body to pivotably drive said inner body and cause the change of position thereof; a spring acting directly on the articulated lever, forcing it to move backwards to a limit determined by an adjustable stop, thus taking the mentioned inner body towards the cold air discharge position, and a unit associated with a heat-expandable element, located in the direction of passage of the discharge air, which has a front portion which can push on the mentioned articulated lever, against the action of the spring, when the temperature of the discharge air rises and said heat-expandable element expands, to thus take the inner body to the hot air discharge position, the mentioned diffuser furthermore includes a stop element, that forms an effective stop with respect to the pivoting travel of the inner body when it is pushed by the expansion of the heat-expandable element through the mentioned articulated lever, the heat-expandable element is configured such that it has a perimetrically thickened portion determining a front portion with which it performs the push on the mentioned articulated lever and a rear portion, characterized in that the stop element, adopting the form of an angle bracket profile, is assembled in the mentioned casing by means of one of its branches with the possibility of adjustable positioning, for which purpose it includes a pivoting securing hole and a slit opening, formed with a certain inclination with respect to the longitudinal direction of the branch of the part, through which there passes a screw or the like for fixing the stop element in the chosen position, whereas the other branch of the angle bracket is projected behind the casing, and in that the rear portion, carrying a spring pressed thereon and supported at the opposite end in a bushing is configured such that it has a tubular portion sized to be coupled in a hole of a support element, such that when the heat-expandable element continues to expand due to the effect of the temperature of the discharge air after the inner body has reached the end of its travel, against the stop, said heat-expandable element can move backwards against the action of the spring, absorbing with the effect of this additional expansion.