An annular prosthesis for a mitral valve that may include a posterior half-ring and an anterior half-ring coupled to each other on a first transverse plane which defines a maximum width section of the prosthesis. The ratio between the distance between the anterior half-ring and the posterior half-ring, as measured along a second plane, perpendicular to the first plane and equidistant to the couplings, and the maximum width of the prosthesis is lower than 3/4.