Abstract: A venous valve prosthesis for transporting a flow of body fluid in a vessel in a predetermined direction includes includes a hollow-cylindrical support structure. A skirt is connected to the support structure and forms a closed, circumferential jacket of the support structure. The prosthesis also includes a valve leaflet arrangement with a first valve leaflet and a second valve leaflet, each being connected to the skirt. A downstream edge of the first valve leaflet and a downstream edge of the second valve leaflet are opposite to each other and configured in such a manner that in a first state of the valve leaflet arrangement they form an opening for blood to flow through in the predetermined direction and in a second state of the valve leaflet arrangement the opening is closed and to prevent a backflow of blood in a direction opposite to the predetermined direction. A ratio of the inner diameter of the support structure to its length in the predetermined direction is at most 1.