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The unique factorization of ideals in a Dedekind domain states that every nonzero proper ideal $I$ of a Dedekind domain $D$ has a factorizationwhere the $P_j$ are distinct nonzero prime ideals and the $n_j$ are positive integers. The prime ideals and their exponents are unique up to reordering. The unit ideal $D$ is the empty product; the zero ideal is excluded.

Write $v_P(I)$ for the prime-ideal valuation in a Dedekind domain, namely the exponent of $P$ in this factorization, with zero assigned when $P$ is absent. The associated containment rule isLarger exponents give smaller ideals, just as higher divisibility gives smaller principal ideals in $\mathbb{Z}$. The theorem concerns unique factorization of ideals; it does not assert unique factorization of elements or that these ideals are principal.

Every ideal of a Dedekind domain is generated by at most two elements. Given a nonzero ideal $I$ and any prescribed nonzero $a\in I$, the Chinese remainder theorem supplies $b\in I$ with $v_P((b))=v_P(I)$ at every prime ideal dividing $(a)$. The prime-ideal valuation in a Dedekind domain then gives $I=(a,b)$.