组蛋白脱乙酰酶类（英语：Histone deacetylases，EC3.5.1.98，简称为HDAC）是能将组蛋白赖氨酸上ε-N-乙酰基（O=C-CH₃）水解掉的一类酶，这使得DNA缠绕组蛋白更加紧密。这点非常重要，因为DNA缠绕着组蛋白，而DNA的表达水平受到组蛋白乙酰化与脱乙酰化水平的影响。该酶的作用与组蛋白乙酰转移酶对冲。HDAC蛋白现在亦被称为赖氨酸脱乙酰酶类（KDAC），这样做的目的是为了突出其功能而非其靶点，因其作用靶点亦包括了非组蛋白的蛋白质类。

Histone deacetylases (EC3.5.1.98, HDAC) are a class of enzymes that remove acetyl groups (O=C-CH₃) from an ε-N-acetyl lysine amino acid on a histone, allowing the histones to wrap the DNA more tightly. This is important because DNA is wrapped around histones, and DNA expression is regulated by acetylation and de-acetylation. Its action is opposite to that of histone acetyltransferase. HDAC proteins are now also called lysine deacetylases (KDAC), to describe their function rather than their target, which also includes non-histone proteins.