The disclosure herein relates to an aircraft fuselage stiffener including a heel, a flange, and a web connecting the heel and the flange, this stiffener comprising a folded sheet extending along the length of the heel, the web and the flange. In addition, to improve the mechanical behavior of the stiffener, the folded sheet includes on the one hand a main portion extending along the length of the heel, the web and the flange, and on the other hand at least one folded-over portion forming a lining of the main portion over at least part of the web and/or the heel and/or the flange.