The present invention relates to an endoprosthesis for a shoulder joint having a stem member (10), extending axially along a first axis (100), with a distal end piece (11) insertable into the humerus of a patient and a proximal end piece (12), a stem head (20) being provided on the proximal end piece (12). In order to be able to achieve an anatomically optimum metaphyseal fit of the endoprosthesis in a simple way, according to the invention the stem member (10) and the stem head (20) are in each case constructed as modular components which are introducible into the patient's body separately from one another during implantation of the endoprosthesis, the stem member (10) having a connecting element (13) at its stem-head-side proximal end (12) and the stem head (20) having at its humeral, distal end (22) a distal connecting element (23) correspondingly constructed so as to be complementary thereto, which connecting elements can be brought into engagement with one another and in the implanted state of the endoprosthesis co-operate with one another so that a force-based connection is formed between stem member (10) and stem head (20).