运动链是一种可活动的机械结构，是构件之间连接（运动副）而构成可相对运动的系统。如果组成运动链的各构件构成首末封闭的系统，则称其为闭式运动链，简称闭链，一般会用在机械中，若未构成则称为开链，多用在机械手中。

运动链会根据各构件间的相对运动为平面运动还是空间运动，可把其分为平面运动链和空间运动链。

Kinematic chain refers to an assembly of rigid bodies connected by joints that is the mathematical model for a mechanical system. As in the familiar use of the word chain, the rigid bodies, or links, are constrained by their connections to other links. An example is the simple open chain formed by links connected in series, like the usual chain, which is the kinematic model for a typical robot manipulator.