Device for fitting an intrauterine device in the uterus of a woman, the intrauterine device being generally T-shaped at rest and comprising a stem at one end (3.1) of which there extend transversely two arms capable of being folded resiliently against the stem, which device comprises: - a rigid inserter which delimits, on the one hand, a through-bore which is centred on a proximodistal axis (X-X) and includes, along that axis, both an intermediate portion (12.2) for substantially coaxially receiving the stem of the intrauterine device to be fitted and a distal terminal portion (12.3) for passage of the stem and of the arms folded against the stem during fitting of the intrauterine device, and, on the other hand, two openings which are transverse to the bore and open in the intermediate portion of the bore, the openings being adapted each to receive one of the arms of the intrauterine device to be fitted when the stem of the intrauterine device is in the intermediate portion of the bore, and also to fold the arms against the stem when the stem is displaced from the intermediate portion to the distal terminal portion of the bore, and - a pusher for moving the intrauterine device relative to the inserter, the pusher including a distal terminal portion (30.2) adapted to be displaced in the bore so as to push the stem of the intrauterine device to be fitted from the intermediate portion (12.2) of the bore out of the inserter via the distal terminal portion (12.3) of the bore, forcing the arms of the intrauterine device to fold against the stem under the action of the openings, the distal terminal portion (30.2) of the pusher delimiting a cavity which is elongated in the longitudinal direction of the pusher and opens at the free end edge of the terminal portion (30.2) of the pusher, and which is adapted to receive in a substantially complementary and coaxial manner a terminal portion (3.3), opposite the arms, of the stem of the intrauterine device to be fitted, characterised in that said cavity has, opposite said free end edge of the terminal portion of the pusher, a flat bottom for axial abutment against the end (3.2), opposite the arms, of said stem. - a rigid inserter which delimits, on the one hand, a through-bore which is centred on a proximodistal axis (X-X) and includes, along that axis, both an intermediate portion (12.2) for substantially coaxially receiving the stem of the intrauterine device to be fitted and a distal terminal portion (12.3) for passage of the stem and of the arms folded against the stem during fitting of the intrauterine device, and, on the other hand, two openings which are transverse to the bore and open in the intermediate portion of the bore, the openings being adapted each to receive one of the arms of the intrauterine device to be fitted when the stem of the intrauterine device is in the intermediate portion of the bore, and also to fold the arms against the stem when the stem is displaced from the intermediate portion to the distal terminal portion of the bore, and - a pusher for moving the intrauterine device relative to the inserter, the pusher including a distal terminal portion (30.2) adapted to be displaced in the bore so as to push the stem of the intrauterine device to be fitted from the intermediate portion (12.2) of the bore out of the inserter via the distal terminal portion (12.3) of the bore, forcing the arms of the intrauterine device to fold against the stem under the action of the openings,