氧化数（英文：Oxidation number）用来表示配位化合物中，所有配体及成配位键的电子对都被去掉后，中心原子所带的电荷数。氧化数这个概念被用于无机化学命名法中。标明氧化数使用罗马数字，并且省略正氧化数的正号。书写时既可以将氧化数写成上标标在元素符号后面，如 Fe，也可将氧化数写在括号内标在元素名称后面，如铁（III），元素名称与括号之间不留空格。

氧化数通常在数值上等于氧化态。但在有些情况下，配体不如中心原子电负性强（如铱膦配合物），因此氧化数与氧化态不相等。

The oxidation state, often called the oxidation number, is an indicator of the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state, which may be positive, negative or zero, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic, with no covalent component. This is never exactly true for real bonds.