Abstract: A protective helmet for sports use, in particular for use by cyclists, comprising a cap structure (2) having a plurality of cap portions which are structurally independent of each other and mutually connected to flexible interconnecting members in such a way that the helmet has at least one overall configuration of minimum dimensions when not worn, with the parts of the cap mutually adjacent to each other, separate from an operating condition having maximum dimensions when the helmet is worn, in which the parts of the cap are held together by interconnecting members in positions at a suitable distance from each other in order to appropriately enclose the user's head is described.