The watermelon is a flowering plant that originated in West Africa, where it can also be found growing in the wild. Citrullus colocynthis has sometimes been considered to be a wild ancestor of the watermelon; its native range extends from north and west Africa to west India. Evidence of the cultivation of both C. lanatus and C. colocynthis in the Nile Valley has been found from the second millennium BC onward, and seeds of both species have been found at Twelfth Dynasty sites and in the tomb of Pharaoh Tutankhamun.

Watermelon fruit is 91% water, contains 6% sugars, and is low in fat. In a 100-gram serving, watermelon fruit supplies 30 calories and low amounts of essential nutrients. Only vitamin C is present in appreciable content at 10% of the Daily Value. Watermelon pulp contains carotenoids, including lycopene.
The amino acid citrulline is produced in watermelon rind.