在物理学里，作用力促使物体绕着转动轴或支点转动的趋向，称为力矩（torque），也就是扭转的力。转动力矩又称为转矩。力矩能够使物体改变其旋转运动。推挤或拖拉涉及到作用力 ，而扭转则涉及到力矩。如图右，力矩等于径向矢量与作用力的叉积。

简略地说，力矩是一种施加于好像螺栓或飞轮一类的物体的扭转力。例如，用扳手的开口箝紧螺栓或螺帽，然后转动扳手，这动作会产生力矩来转动螺栓或螺帽。

根据国际单位制，力矩的单位是牛顿米。本物理量非能量，因此不能以焦耳（J）作单位；根据英制单位，力矩的单位则是英尺磅。力矩的表示符号是希腊字母，或。

Torque, moment, or moment of force (see the terminology below) is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. Mathematically, torque is defined as the cross product of the position vector of the point where the force is applied (distance vector) and the force vector, which tends to produce rotation.