Spodoptera praefica, the western yellow-striped armyworm, is a moth of the family Noctuidae found from British Columbia to California, east to Utah, and north to Alberta.

As of 4 October 2021[update] it is absent from the EPPO (European and Mediterranean Plant Protection Organization) area, but is considered a high risk for invasion there.

It is similar in appearance to Spodoptera ornithogalli, but S. praefica's fore-wings are paler and lack the blurry white stripe.

The hind-wings of S. praefica are white or gray and have a small brown dot on the ventral side.

[1][2] The larvae are black with yellow stripes and an inverted "y" marking on the head.