氢氧化钠，又称烧碱和苛性钠，化学式为NaOH，是一种具有高腐蚀性的强碱，一般为白色片状或颗粒，能与水混溶生成碱性溶液，另也能溶解于甲醇及乙醇。此碱性物具有潮解性，会吸收空气里的水蒸气，亦会吸取二氧化碳等酸性气体。

氢氧化钠为常用的化学品之一。其应用广泛，为很多工业过程的必需品：常用于制造木浆纸张、纺织品、肥皂及其他清洁剂等，另也用于家居碱性通渠用品。2004年全球总共制造了六千万吨的氢氧化钠，而总消耗量为五千一百万吨。

Sodium hydroxide (NaOH), also known as lye and caustic soda, is an inorganic compound. It is a white solid and highly caustic metallic base and alkali salt of sodium which is available in pellets, flakes, granules, and as prepared solutions at a number of different concentrations. Sodium hydroxide forms an approximately 50% (by weight) saturated solution with water.