Antiguraleus costatus is a species of sea snail, a marine gastropod mollusk in the family Mangeliidae.

(Original description) The small, thin shell has an elongate-ovate shape.

The sculpture shows narrow, sharp radials, elevated riblets, becoming closer and smaller as growth proceeds, and vanishing on the base.

The outer lip is thin, not inflected, with a wide and shallow sinus.

[2] This marine species is endemic to Australia and occurs off New South Wales.