The objective of the proposed research is to design, fabricate, and measure novel RF devices based on vanadium dioxide (VO2) for wideband switching and nonlinearity-based nonreciprocity. VO2 is a phase-change material (PCM) that exhibits a sharp, reversible change in conductivity of up to five orders of magnitude at 68 °C. Ultrawideband switches are demonstrated by exciting this insulator-metal transition (IMT) using a laser, circumventing the need for on-wafer microheaters that add parasitic capacitance and limit bandwidth. The first generation of switches have been demonstrated up to 65 GHz, and the second generation of switches show a bandwidth of dc–330 GHz. The IMT can also be excited by an impinging RF wave, allowing for the realization of nonlinear systems based on VO2. A compact model for the VO2 switch is presented, and concepts for nonlinear, nonreciprocal VO2 components are proposed. This study aims to demonstrate fully passive nonreciprocal microwave devices based on nonlinear VO2 for the first time.