Hip prosthesis comprising: a prosthetic neck, provided with means for coupling with a morse cone type spherical head, a femoral stem that can be inserted within the medullar channel of a patient femur, the femoral stem comprising a front face, a rear face and lateral and medial faces, the stem including a base, the medial face of said femoral stem being joined with the prosthetic neck by a proximal portion having an arcuate shape, said front and rear faces of the femoral stem being provided with substantially longitudinal lateral reliefs (60, 61) on the base, said reliefs (60, 61) extending substantially from a proximal end of the femoral stem to a distal end, so that said stem can be fixed to the bone tissue by pressure; said prosthesis characterized in that: the cross section of each of said longitudinal reliefs (60, 61) has a peak portion, 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 less than said first angle (c), and grooves provided between said longitudinal reliefs (60, 61), that can be homogeneously filled with spongious bone tissue, said base having the same profile as defined by the peaks of said longitudinal reliefs (60, 61) in a transverse plane (A-A) of the prosthetic femoral stem, said femoral stem having a main axis, said main axis being the rectilinear line connecting the apex of the distal end of said femoral stem and the point in which said femoral stem joins with said prosthetic neck, and a main relief of each of the front and rear sides, has a height from a central coronal plane of the femoral stem greater than the other longitudinal reliefs. a prosthetic neck, provided with means for coupling with a morse cone type spherical head, a femoral stem that can be inserted within the medullar channel of a patient femur, the femoral stem comprising a front face, a rear face and lateral and medial faces, the stem including a base, the medial face of said femoral stem being joined with the prosthetic neck by a proximal portion having an arcuate shape, said front and rear faces of the femoral stem being provided with substantially longitudinal lateral reliefs (60, 61) on the base, said reliefs (60, 61) extending substantially from a proximal end of the femoral stem to a distal end, so that said stem can be fixed to the bone tissue by pressure; said prosthesis characterized in that: the cross section of each of said longitudinal reliefs (60, 61) has a peak portion, 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 less than said first angle (c), and grooves provided between said longitudinal reliefs (60, 61), that can be homogeneously filled with spongious bone tissue, the cross section of each of said longitudinal reliefs (60, 61) has a peak portion, 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 less than said first angle (c), and grooves provided between said longitudinal reliefs (60, 61), that can be homogeneously filled with spongious bone tissue, said base having the same profile as defined by the peaks of said longitudinal reliefs (60, 61) in a transverse plane (A-A) of the prosthetic femoral stem, said femoral stem having a main axis, said main axis being the rectilinear line connecting the apex of the distal end of said femoral stem and the point in which said femoral stem joins with said prosthetic neck, and a main relief of each of the front and rear sides, has a height from a central coronal plane of the femoral stem greater than the other longitudinal reliefs.