A shape-memory saddle structure, particularly for pedal driven vehicles, comprising a substantially rigid or semirigid support frame (2), means (4) for connecting said frame (2) to a vehicle, a yielding pad (7) secured to the upper face (S) of the frame (2), and a cover layer (5) laid over the yielding pad (3). The frame (2) has one or more portions (6, 6′, 6″) having a different deformability from that of the rest of the frame (2). The portions (6, 6′, 6″) include at least one membrane of fibrous material, which is susceptible to permanent deformation in response to a compression stress by a user, so as to take a deformed configuration. The membrane (7) is closely joined to at least one layer of elastomeric material (8), which is adapted to locally change the rigidity of the membrane (7) by elastically holding it at least partly in the deformed configuration, to customize the frame (2) to the specific user's body.