Abstract: The invention relates to a THz sensor (2) for measuring an object to be measured (6), in particular, a pipe, the THz sensor (2) comprising: a THz transceiver (10) for emitting and receiving THz radiation, a lens (14) for bundling the THz radiation emitted by the THz transceiver (10) and emitting a THz transmission beam (8) along the optical axis (A) and for receiving a THz reflection beam (15), a support device (11), on which the lens (14) and/or the THz transceiver (10) is accommodated or fastened. Hereby, it is provided that a THz radiation-influencing compensation formation for modifying and/or reducing incident THz radiation is provided in a compensation area between the lens and the support device (11).