Stirrup (10, 110) for horse-riding saddles, comprising: - a support element (11, 111), to support a user's foot, - and an open arch extending from the opposite ends of said support element, said open arch in turn comprising: - a first load-bearing half-arch (13, 113) extending from a first lateral portion of said support element (11, 111) and comprising an attachment portion configured for fastening a stirrup strap, - and a second containment half-arch (16, 116), extending from a second lateral portion of said support element (11, 111), opposite to said first lateral portion, said second half-arch (16, 116) comprising a lower part (18, 118) configured to be constrained to said support element (11, 111), and an upper part (19, 119) extending from said lower part (18, 118) up to the proximity of said attachment portion, said second half-arch (16, 116) comprising a single body of elastically deformable plastic material defining said lower part (18, 118) and said upper part (19, 119), said upper part (19, 119) extending along a development curved line, said upper part (19, 119) extending from its lower end, being a part of the single body, the lower end of which is located substantially in correspondence with an upper surface of said support element (11, 111), along said curved line, up to an upper end thereof positioned in proximity to, or in contact with, a facing end of said attachment portion, the cross-sectional area of said upper part (19, 119) decreasing in the direction which runs from said lower end to said upper end, characterized in that said upper part (19, 119) has a transversal section at any of its points, orthogonal to said development curved line, having a circular or oval profile. - a support element (11, 111), to support a user's foot, - and an open arch extending from the opposite ends of said support element, said open arch in turn comprising: - a first load-bearing half-arch (13, 113) extending from a first lateral portion of said support element (11, 111) and comprising an attachment portion configured for fastening a stirrup strap, - and a second containment half-arch (16, 116), extending from a second lateral portion of said support element (11, 111), opposite to said first lateral portion, said second half-arch (16, 116) comprising a lower part (18, 118) configured to be constrained to said support element (11, 111), and an upper part (19, 119) extending from said lower part (18, 118) up to the proximity of said attachment portion, - a first load-bearing half-arch (13, 113) extending from a first lateral portion of said support element (11, 111) and comprising an attachment portion configured for fastening a stirrup strap, - and a second containment half-arch (16, 116), extending from a second lateral portion of said support element (11, 111), opposite to said first lateral portion, said second half-arch (16, 116) comprising a lower part (18, 118) configured to be constrained to said support element (11, 111), and an upper part (19, 119) extending from said lower part (18, 118) up to the proximity of said attachment portion, said second half-arch (16, 116) comprising a single body of elastically deformable plastic material defining said lower part (18, 118) and said upper part (19, 119), said upper part (19, 119) extending along a development curved line, said upper part (19, 119) extending from its lower end, being a part of the single body, the lower end of which is located substantially in correspondence with an upper surface of said support element (11, 111), along said curved line, up to an upper end thereof positioned in proximity to, or in contact with, a facing end of said attachment portion, the cross-sectional area of said upper part (19, 119) decreasing in the direction which runs from said lower end to said upper end, characterized in that said upper part (19, 119) has a transversal section at any of its points, orthogonal to said development curved line, having a circular or oval profile.