A noncontact cryogenic microwave measurement system has been developed for the characterization of passive and active superconducting devices by means of an unloaded quality factor measurement technique. The measurement system was designed specifically for the characterization of planar thin film resonant structures as a function of temperature (4–300 K), frequency (100 MHz–26.5 GHz), and dc voltage bias (≤100 V). It has been used for basic device studies of novel active superconducting lumped components made of metal‐oxide superconductor/insulator heterostructures.