Ascalaphus sinister is a species of owlfly from northern India.

The thorax is covered in brown hairs, with yellow markings on the sides and ventral surface and a yellow stripe running down the dorsum.

The antennae are rust red and not as long as the wings.

The elongate abdomen is saffron yellow with two black stripes down the back and a number of black streaks along the sides.

The bursa copulatrix and receptaculum seminis are relatively proximate, with the latter being sclerotized and wrinkled.