What is described is a turbine guide vane having a guide vane leaf and with a radially outer platform connected to the guide vane leaf and having a platform surface which faces radially away from the guide vane leaf and on which a connecting structure is provided for fastening the guide vane to a supporting structure which has side wall portions which project radially beyond the platform surface and delimit an inner cavity and on which is provided at least in portions a joining contour which can be inserted into a reception shape countercontoured within the supporting structure. At least one seal is provided between the connecting structure and the supporting structure.