S. occidentalis may refer to: Sarcoscypha occidentalis, the stalked scarlet cup or western scarlet cup, a mushroom species Sceloporus occidentalis, the Western fence lizard, a reptile species common in California Senna occidentalis, a pantropical plant species Simosthenurus occidentalis, the short-faced kangaroo, an extinct marsupial species Sorbus occidentalis, a tree species in the genus Sorbus found in Western North America
See also List of Latin and Greek words commonly used in systematic names#O