Monoplex parthenopeus, the giant triton or giant hairy triton, is a species of sea snail, a marine gastropod mollusk in the family Cymatiidae. It preys on other molluscs.

Fossil records: This species have been recorded as fossils from the Miocene to the Quaternary (from 15.97 to 0.0 million years ago).

Distribution: This species occurs worldwide including:

• The Western Atlantic Ocean
• New Zealand

 The maximum recorded shell length is 180 mm.

Habitat: Trawled 40–60 m. off Akwa Ibom State, Nigeria.

Minimum recorded depth is 0 m. Maximum recorded depth is 75 m.

Life cycle: Hairy tritons are notable for having particularly long planktonic periods. The veliger larvae remain in the plankton for nearly 300 days, dispersing as far as 4000 km. This is the longest known larval duration and dispersal distance of any marine invertebrate which occurs along the west coast of North America.