在抽象代数中，域（Field）是一种可进行加、减、乘和除运算的代数结构。域的概念是数域以及四则运算的推广。

域是环的一种。域和一般的环的区别在于域要求它的元素可以进行除法运算，这等价于说每个非零的元素都要有乘法逆元。同时，在现代的定义中，域中的元素关于乘法要是可交换的。简单来说，域是乘法可交换的除环。乘法非交换的除环则称为体（Körper, corps），或者反称域（skew field）。在比较旧的定义中，除环被称为“域”，而现代意义上的域被称为“交换域”。

In mathematics, a field is one of the fundamental algebraic structures used in abstract algebra. It is a nonzero commutative division ring, or equivalently a ring whose nonzero elements form an abelian group under multiplication. As such it is an algebraic structure with notions of addition, subtraction, multiplication, and division satisfying the appropriate abelian group equations and distributive law. The most commonly used fields are the field of real numbers, the field of complex numbers, and the field of rational numbers, but there are also finite fields, algebraic function fields, algebraic number fields, p-adic fields, and so forth.