The invention relates to a prosthesis shaft retaining device and a system for securing a prosthesis shaft (4) to an upper extremity, comprising a securing part (2) that can be guided along the torso (1) below the axilla of the contralateral, unprovided side of a patient, and a coupling element (9) which can be secured to the prosthesis shaft (4) and connected to the securing part (2), wherein the coupling element (9) is displaceably mounted on the securing part (2).