Graphium porthaon, the coastal swordtail, cream-striped swordtail or dark swordtail, is a species of butterfly in the family Papilionidae, found in tropical western Africa.

The wingspan is 55–60 mm in males and 60–65 mm in females. External images from Royal Museum of Central Africa.The species has continuous broods during warmer months.

The larvae feed on Artabotrys monteiroae, Annona, Uvaria, Friesodielsia obovata, Cleistochlamys kirkii, Monodora junodii, Monanthotaxis caffra, Uvaria caffra, and Uvaria kirkii.

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