Colias occidentalis, the western sulphur or golden sulphur, is a butterfly in the family Pieridae found in North America. Its range includes the Pacific Northwest and parts of British Columbia. Flight period is from late May until early July. Its habitats include ocean bluffs, forest openings, mountain slopes, and subalpine meadows. Wingspan is from 50 millimetres (2.0 in) to 53 millimetres (2.1 in). Larvae feed on Vicia spp., Lupinus spp., Lathyrus spp., and Thermopsis spp.