A hair trimmer is disclosed, comprising a fixed cutting element having teeth on the front side thereof, and a mobile cutting element which has teeth on the front side thereof and is oscillable in relation to the fixed cutting element, so that, when the hair trimmer is used, hairs reaching between the teeth of the fixed cutting element and the mobile cutting element are cut off. The hair trimmer also has a protective support which has teeth on its front side, is arranged on the fixed cutting element, and used to place the hair trimmer on the skin of the user. The teeth of the protective support lock with the teeth of the fixed cutting element on the front side or slightly extend over the teeth, and the teeth of the protective support lie on the fixed cutting element, essentially without gaps.