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.

The flight period is from late May until early July. Its habitats include ocean bluffs, forest openings, mountain slopes, and subalpine meadows.

Its wingspan ranges from 50 millimetres (2.0 in) to 53 millimetres (2.1 in).

Its larvae feed on flowers like the Vicia spp., Lupinus spp., Lathyrus spp., and Thermopsis spp.

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