Calagrassor poppei is a species of sea snail, a marine gastropod mollusk in the family Eosiphonidae, the true whelks and their allies.

[2] A carnivorous and predatory [3] sea snail found in the Philippines, this mollusk has a shell size that averages 16.6mm (0.65 inches) [4] Common name: Poppe's delicate whelk[5] named for Guido T. Poppe, conchologist and museum-quality collector, photographer, and author active in the field since childhood.

The species is known to attain a size of 50+ mm.

An operculum is present.

This marine species occurs off the Philippines.