莲花效应（lotus effect），也称作荷叶效应，是指莲叶表面具有超疏水性以及自洁（self-cleaning）的特性。在东方文化里，莲花是纯净的象征。虽然，莲花喜欢生长在泥泞的湿地，但其叶子和花仍保持干净，这就是自洁的效果。植物学家研究莲叶表面发现它们有一个自然洁净的机制。

莲叶的微观结构和表面化学意味着不会被水弄湿；水滴在叶片表面就如水银一般，并且可以带走污泥、小昆虫及污染物。而且，水滴在芋头叶子亦有相似的行为。

一些奈米科技学家正在开发一些方法，使涂料、屋瓦、纺织品和其它表面可保持干燥和干净，就如莲叶表面的方式相似。通常使用氟化物或硅处理表面而达到此效果；利用葡萄糖和蔗糖化合成聚乙二醇亦可达到此效果。有自洁效应的新涂料，目前已被发展，甚至有自洁功能的玻璃板也已经进入市场，使用于温室的屋顶等。

The lotus effect refers to self-cleaning properties that are a result of very high water repellence (superhydrophobicity), as exhibited by the leaves of the lotus flower (Nelumbo). Dirt particles are picked up by water droplets due to the micro- and nanoscopic architecture on the surface, which minimizes the droplet's adhesion to that surface. Superhydrophobicity and self-cleaning properties are also found in other plants, such as Tropaeolum (nasturtium), Opuntia (prickly pear), Alchemilla, cane, and also on the wings of certain insects.