A measuring sensor, in particular for determining the oxygen content in exhaust gases of internal combustion engines, having a sensor element fixed in gastight fashion in a metal housing (14) and having a sealing flange (60) mounted on the housing (14) and resting on a sealing seat (76) embodied in an exhaust system (11). A union nut (80) is guided over onto the housing (14) and can be screwed into a thread (78) of an opening (70) provided in the exhaust system (11) and presses the sealing flange (60) against the sealing seat (76). The housing (14) has a housing part (12) on the side toward the gas to be measured and a further housing part (13) on the side toward the connection, and the sealing flange (60) is disposed on the housing part (13) on the side toward the connection and is shaped from the material of the housing part (13) on the side toward the connection.