基本相互作用（fundamental interaction），为物质间最基本的相互作用，常称为自然界四力或宇宙基本力。迄今为止观察到的所有关于物质的物理现象，在物理学中都可借助这四种基本相互作用的机制得到描述和解释。

大统一理论认为：强相互作用、弱相互作用和电磁相互作用可以统一成一种相互作用，目前统一弱相互作用和电磁相互作用的电弱统一理论已经获得实验证实。

Fundamental interactions, also known as fundamental forces, are the interactions in physical systems that do not appear to be reducible to more basic interactions. There are four conventionally accepted fundamental interactions—gravitational, electromagnetic, strong nuclear, and weak nuclear. Each one is understood as the dynamics of a field. The gravitational force is modelled as a continuous classical field. The other three are each modelled as discrete quantum fields, and exhibit a measurable unit or elementary particle.