The yellow water-lily, cow lily, or yellow pond-lily, is an aquatic plant of the family Nymphaeaceae, native to Eurasia and North America. It grows in eutrophic freshwater beds, with its roots fixed into the ground and its leaves floating on the water's surface.

The plant's inflorescence is a solitary, terminal hermaphrodite flower, pollinated by insects, which blooms from June to September in the Northern Hemisphere. The flower is followed by achenes which are distributed by the water current. It can grow in water up to 40 cm (16 in) deep.

Spatterdock was long used in traditional medicine, with the root applied to the skin and/or both the root and seeds eaten for a variety of conditions. The seeds are edible, and can be ground into flour. The root is edible too, but can prove to be incredibly bitter in some plants.