流体动力学（Fluid dynamics）是流体力学的一门子学科。流体动力学研究的对象是运动中的流体（含液体和气体）的状态与规律。流体动力学底下的子学科包括有空气动力学和液体动力学。

解决一个典型的流体动力学问题，需要计算流体的多项特性，主要包括速度、压力、密度、温度。

流体动力学有很大的应用，比如在预测天气，计算飞机所受的力和力矩，输油管线中石油的流率等方面上。其中的的一些原理甚至运用在交通工程，因交通运输本身可被视为一连续流体运动。

In physics, fluid dynamics is a subdiscipline of fluid mechanics that deals with fluid flow—the natural science of fluids (liquids and gases) in motion. It has several subdisciplines itself, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation. Some of its principles are even used in traffic engineering, where traffic is treated as a continuous fluid, and crowd dynamics.