Nymphaea nouchali, often known by its synonym Nymphaea stellata, or by common names blue lotus, star lotus, red water lily, dwarf aquarium lily, blue water lily, blue star water lily or manel flower, is a water lily of genus Nymphaea. It is native to southern and eastern parts of Asia, and is the national flower of Bangladesh and Sri Lanka. In Sanskrit it is called utpala. This species is usually considered to include the blue Egyptian lotus N. nouchali var. caerulea. In the past, taxonomic confusion has occurred, with the name Nymphaea nouchali incorrectly applied to Nymphaea pubescens.

Nymphaea is a genus of hardy and tender aquatic plants in the family Nymphaeaceae. The genus has a cosmopolitan distribution. Many species are cultivated as ornamental plants, and many cultivars have been bred. Some taxa occur as introduced species where they are not native, and some are weeds. Plants of the genus are known commonly as water lilies, or waterlilies in the United Kingdom. The genus name is from the Greek νυμφαία, nymphaia and the Latin nymphaea, which mean "water lily" and were inspired by the nymphs of Greek and Latin mythology.