The present invention refers to an annular prosthesis for mitral valve. In one of its embodiments the annular prosthesis for mitral valve is made up of 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, characterized in that the ratio between the distance between said anterior half-ring and said posterior half-ring, as measured along a second plane, perpendicular to said first plane and equidistant to said couplings, and said maximum width of the prosthesis is lower than ¾.