格拉晓夫数（Grashof number，Gr数）为一无量纲的纯量，常用在流体力学及热传导中。格拉晓夫数可以视为流体浮力与粘性力的比值，是研究自然对流时重要的参数。格拉晓夫数的命名是源自德国工程师Franz Grashof。

其中下标的L及D表示格拉晓夫数参考长度的来源。

The Grashof number (Gr) is a dimensionless number in fluid dynamics and heat transfer which approximates the ratio of the buoyancy to viscous force acting on a fluid. It frequently arises in the study of situations involving natural convection. It is named after the German engineer Franz Grashof.