A linear actuator for gates, doors or similar has an actuator arm (1) which is articulated to a support (3) around a vertical axis (15) and be raisable angularly around a horizontal inclination axis (16). The actuator arm (1) has a screw (7) which is operated by an electric motor (11) and a running nutscrew (8) articulated to the gate wing (5) by a leadnut holder (18) in which the nutscrew (8) is housed in a manner turning around an axis horizontal and transversal to the actuator arm (1). The leadnut holder (18) has a vertical lower articulation pivot (20) which engages from above in a turning manner in a bush (22) fastened to the wing (5). In an emergency the actuator is disengaged from the gate wing (5) by raising the actuator arm (1) angularly around its inclination axis (16) and extracting upward the articulation pivot (20) of the leadnut holder (18) from the bush (22).