A protective helmet for protecting the head of a user, characterized in that it comprises an enveloping structure consisting of an inner component (1), at least one intermediate component (2) and an outer base component (3) having an annular configuration, where the components (1, 2, 3) are coupled one inside the other, can move in relation to each other from a retracted position to a deployed position and vice versa, and create a space, in a deployed position, corresponding to the part of the user's head that is inside the helmet.