Pachysphinx modesta (modest sphinx, poplar sphinx) is a moth of the family Sphingidae. It ranges from the southern United States up and throughout Canada. Adults are on wing from mid June to mid July in Canada. In the northern part of the range, there is one generation with adults on wing from may to July. Farther south, there might be two generations per year. The larvae feed on poplar, willow and cottonwood species.