The present invention relates to a hip prosthesis (1) comprising a femoral stem (20) that can be inserted within the medullar channel of a patient femur, the medial side (21) of said femoral stem (20) having, in the proximal portion (40), the shape of an arc, said femoral stem (20) being provided with substantially longitudinal lateral reliefs (60, 61), so that said stem (20) can be fixed to the bone tissue by pressure, and a prosthetic neck (30), provided with means for coupling with a morse cone type spherical head (31), said prosthesis (1) being characterized in that the cross section of said longitudinal reliefs (60, 61) has an apex portion (60′), having the lateral walls included within a first angle (c), and a base portion having the lateral walls included within a second angle (d), which is minor or equal to said first angle (c), and in that grooves (63) are provided between said longitudinal reliefs (60, 61), that can be homogeneously filled with spongious bone tissue.