ABSTRACT.Purple ammannia (Ammannia coccinea Rottb.) is an exotic weed originated from North America. It was known to be a noxious weed in a rice paddy field for the competition with rice. We investigated its distribution and habitat types in Korea to obtain basic data for the management plan of this species. Although purple ammannia is currently not a dominant species in natural habitats, its nationwide distribution was found in our study. We categorized the types of its habitats as margins of rice paddies, abandoned paddy fields, riverine wetlands and reservoirs. Particularly, purple ammannia plants were frequently located along banks of irrigation channels that ran through rice paddies and surrounding wetlands. Because they mainly occurred along the direction of water flow, we considered that the plants have spread along water courses. A total of 69 vascular plant taxa was identified at the habitats of purple ammannia. The largest group of life form among purple ammannia population was therophytes, which indicates that purple ammannia mostly grow in the disturbed habitats.