A reconfigurable sensing antenna (RSA) concept is presented in this letter, where a physical sensor is integrated into a reconfigurable antenna as the control unit. The basic structure and operation principle of the RSA are described in details. To illustrate this RSA concept, a slotted patch antenna with temperature sensation is designed, fabricated, and tested. In this design, distilled water is integrated into the antenna substrate as the sensing material because its permittivity changes with temperature. Thus, the antenna frequency is reconfigured according to the environmental temperature. The measurement results demonstrate an effective sensing range from 17
to 70
. Due to the passive and low-cost features, the proposed RSA has a promising potential in wireless sensing network applications.