WD-40（NASDAQ：WDFC）是一種註冊商標的多用途潤滑防鏽石油製劑品牌，由總公司位於美國加州聖地牙哥市的WD-40公司製造銷售。WD-40原本被發展作為一種隔水抗鏽劑，但產品上市後人們漸漸發現它也可以被當作輕度潤滑用油或是溶劑、除膠劑、清潔劑，進而漸漸轉變用途。由於其多用途的特性，WD-40是一種很難被嚴格歸類或定義的特殊商品，但在全世界都擁有極高的知名度。

It was developed in 1953 by Dr. Norm Larsen, founder of the Rocket Chemical Company, in San Diego, California. WD-40, abbreviated from the phrase "Water Displacement, 40th formula,"was originally designed to repel water and prevent corrosion, and later was found to have numerous household uses.

Larsen was attempting to create a formula to prevent corrosion in nuclear missiles, by displacing the standing water that causes it. He claims he arrived at a successful formula on his 40th attempt. WD-40 is primarily composed of various hydrocarbons.

WD-40 was first used by Convair to protect the outer skin and, more importantly, the paper-thin "balloon tanks" of the Atlas missile from rust and corrosion. These stainless steel fuel tanks were so thin that, when empty, they had to be kept inflated with nitrogen gas to prevent their collapse.

WD-40 first became commercially available on store shelves in San Diego, California in 1958.