Nymphaeaceae is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate and tropical climates around the world. The family contains five generawith about 70 known species. Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on or emergent from the surface. Leaves are round, with a radial notch in Nymphaea and Nuphar, but fully circular in Victoria and Euryale.

Water lilies are a well-studied clade of plants because their large flowers with multiple unspecialized parts were initially considered to represent the floral pattern of the earliest flowering plants, and later genetic studies confirmed their evolutionary position as basal angiosperms.