Xylophanes fosteri is a moth of the family Sphingidae.

Differences in the forewing upperside are two short dashes distal to the discal spot which are blurred into a diffuse patch.

The first and second postmedian lines are merged into a broad band at the inner margin of the wing, gradually diverging towards the apex but disappearing later.

The fourth and fifth postmedian lines are parallel at first, but divergent later and then disappearing.

The fourth line is represented only by vein dots.