Keesingia gigas, the "giant" (Greek gigas) Keesingia, is one of two new species of Irukandji jellyfish, the only one of the genus Keesingia in the Alatinid family. Found off the north-west coast of Western Australia, the species is able to deliver an extremely deadly sting which can cause the victim to experience the Irukandji syndrome which can cause pain, nausea, vomiting and in some rare instances stroke or heart failure.