动态平衡发生于两个逆向但同步的过程当中。首先见于化学，但后来在生态学、经济学而至政治学等均有所应用。

在一个可逆的化学反应中，当正向反应及逆向反应的反应速率相等时就会达致动态平衡。在这个状态下不论生成物及反应物的浓度均没有改变，动态一词意指两个反应仍然在持续进行而非停滞，但刚好两者的速率相等，致使各自的浓度均没有改变，达致平衡状态。

For the economic concept, see Dynamic equilibrium (economics)

In chemistry, A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. It is a particular example of a system in a steady state. In thermodynamics a closed system is in thermodynamic equilibrium when reactions occur at such rates that the composition of the mixture does not change with time. Reactions do in fact occur, sometimes vigorously, but to such an extent that changes in composition cannot be observed. Equilibrium constants can be expressed in terms of the rate constants for elementary reactions.