Brasenia is a genus belonging to the family Cabombaceae, consisting of one species, Brasenia schreberi, commonly known as watershield. It is widely distributed in North America, the West Indies, northern South America (Venezuela, Guyana), eastern Asia (China, Japan, Korea, Primorye), Australia, the Indian subcontinent, and parts of Africa.

Brasenia is a perennial aquatic plant with floating, peltate leaves and rhizomatous stems. It is identified by its bright green leaves, small purple flowers that bloom from June through September, and a thick mucilage that covers all of the underwater organs, including the underside of the leaves, stems, and developing buds. This mucilage may be an anti-herbivore defence trait, perhaps to deter snail grazing. It grows in shallow water of lakes, rivers and beaver ponds, particularly those with somewhat acidic water.