在数学中，三次互反律是关于模代数中两个对应的三次方程的可解性之间的关系的结论和定理。

三次互反律最常使用艾森斯坦整数进行表述。艾森斯坦整数是指由形如 的复数组成的环，记作 。其中 和 是整数， 为三次单位根：

Cubic reciprocity is a collection of theorems in elementary and algebraic number theory that state conditions under which the congruence x ≡ p (mod q) is solvable; the word "reciprocity" comes from the form of the main theorem, which states that if p and q are primary numbers in the ring of Eisenstein integers, both coprime to 3, the congruence x ≡ p (mod q) is solvable if and only if x ≡ q (mod p) is solvable.