咕啉（Corrin）是一种杂环分子。在内圈的十五元环里，有四个氮原子作为配体。

因为它在维生素B12中与Co(III)离子形成四个配位键，具有中心（Core）地位，故得名。

Corrin is an heterocyclic compound. It is the parent macrocycle related to substituted derivative that is found in vitamin B₁₂. Its name reflects that it is the "core" of vitamin B₁₂ (cobalamins).