NRF2 expression and nuclear localization were reduced in PH lungs and hypoxia-exposed cells, whereas Omaveloxolone restored NRF2 activity and increased downstream antioxidant enzymes. In endothelial cells, Omaveloxolone reduced oxidative stress, suppressed inflammatory signaling, and inhibited endothelial-to-mesenchymal transition. In smooth muscle cells, it attenuated oxidative stress and normalized abnormal proliferation, migration, and apoptosis. Omaveloxolone reduced HIF (hypoxia-inducible factor)-2α accumulation in endothelial cells and inhibited HIF-1α stabilization in smooth muscle cells. NRF2 knockdown attenuated these effects, supporting pathway dependency. Omaveloxolone attenuated PH, reduced right ventricular hypertrophy and vascular remodeling, and improved right ventricular function across hypoxia, monocrotaline, and sugen/hypoxia models under both preventive and therapeutic regimens.