西瓜（学名：Citrullus lanatus），古称寒瓜，是葫芦科西瓜属的一种植物或其果实。原产于非洲，是一种双子叶开花植物，形状像藤蔓，叶子呈羽毛状。它所结出的果实是假果，且属于植物学家称为假浆果的一类。果实外皮光滑，呈绿色或黄色有花纹，果瓤多汁为红色或黄色。西瓜的产量十分丰富，差不多每一株藤就可以结出达100个果实。但西瓜种植时怕水，水浇多了之后容易导致甜度降低，水伤。

西瓜可分为野生或种植的。野生的西瓜称为野生西瓜种质（学名：Citrullus lanatus var. citroides），瓢为白色，而种植的西瓜则称为栽培西瓜品系（学名：Citrullus lanatus var. lanatus）。

Watermelon (Citrullus lanatus var. lanatus, family Cucurbitaceae) is a vine-like (scrambler and trailer) flowering plant originally from southern Africa. It is a large, sprawling annual plant with coarse, hairy pinnately-lobed leaves and white to yellow flowers. It is grown for its edible fruit, also known as a watermelon, which is a special kind of berry botanically called a pepo. The fruit has a smooth hard rind, usually green with dark green stripes or yellow spots, and a juicy, sweet interior flesh, usually deep red to pink, but sometimes orange, yellow, or white, with many seeds.