Crinum thaianum, Common name Thai Onion plant or Water onion, is an emergent plant species endemic to coastal plain of southern Thailand in Ranong and Phang Nga Provinces. Its natural habitat is along the banks of running streams, where its roots and bulb are submerged but the flowering holds the umbel of large, showy flowers above the surface. This natural habits make it a wonderful addition for tropical aquaria, and it is sold in many lands to be used in decorating displays of tropical fish. In nature, however, the species is threatened and diminishing in numbers due to habitat destruction.