A microelectromechanical systems (MEMS) capacitive-type passive wireless pressure sensor designed to operate in harsh environments at temperatures up to 1000 °C is presented. The pressure sensor has a sapphire-based diaphragm and structural body, and a platinum-based capacitive element. The capacitive element is configured as a part of a slot patch antenna that is designed to operate in a far-field sensing mechanism with a Ku-band electrical resonant frequency of 15 GHz. The electrical ground plane resides on the backside of the diaphragm, which deflects in response to an applied pressure. The electrical resonant frequency of the pressure sensor changes as a function of the applied pressure to the diaphragm. An increase in the applied pressure, for example, results in a decrease in the electrical resonant frequency. The sensitivity of the pressure sensor is related to the change in applied pressure to the change in the electrical resonant frequency. Three proof-of-concept dynamic pressure sensors are reported using silicon-based diaphragms with antenna diameters of 5.6, 5.7, and 5.8 mm, and measured sensitivities of 2.2, 2.2, and 5.1 kHz/Pa, respectively, up to 900 Pa. In addition, three proof-of-concept static pressure sensors are reported with corresponding measured sensitivities of 3.4, 3.1, and 2.5 kHz/Pa up to 900 Pa. A high-temperature dynamic pressure sensor designed for harsh environments is also reported using a sapphire-based diaphragm with an antenna diameter of 3.8 mm and measured sensitivity of 21.7 kHz/Pa up to 800 Pa.