泊肃叶定律（Poiseuille's law）也称为帕醉定律、哈根-泊肃叶定律（Hagen-Poiseuille's law）、哈根-帕醉方程（Hagen-Poiseuille's equation），是描述流体流经细管（如血管和导尿管等）所产生的压力损失，压力损失和体积流率、动黏度和管长的乘积成正比，和管径的四次方成反比例。此定律适用于不可压缩、不具有加速度、层流稳定且长于管径的牛顿流体。泊肃叶定律是让·泊肃叶于1838年和戈特希尔夫·哈根于1838和1839年分别实验独立发现的，并于1840年和1846年发表。

In nonideal fluid dynamics, the Hagen–Poiseuille equation, also known as the Hagen–Poiseuille law, Poiseuille law or Poiseuille equation, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section. It can be successfully applied to air flow in lung alveoli, for the flow through a drinking straw or through a hypodermic needle. It was experimentally derived independently by Gotthilf Heinrich Ludwig Hagen in 1839 and Jean Léonard Marie Poiseuille in 1838, and published by Poiseuille in 1840 and 1846.