The present invention relates to a prosthesis (1) for repairing an inguinal hernia defect comprising:a piece (2) of biocompatible material having a preformed three-dimensional shape, including: a first portion (3) forming a partial spherical cap surface (8) shaped and dimensioned so as to substantially conform to the shape of the anterior abdominal wall,a second portion (4) extending from an inferior edge of said first portion and forming a wavy-shaped wall (9), shaped and dimensioned so as to substantially conform to the shape of the psoas muscle,characterized in that said piece (2) further comprises:a third portion (5) forming an arched part (10) extending longitudinally in the inferior direction from a medial inferior corner (3a) of said first portion, said arched part extending radially substantially in the front direction, said third portion being intended to face the medial inferior area of the inguinal anatomy.
