隐变量理论又称隐变量理论，是由物理学家质疑量子力学完备性而提出的替代理论。历史上随着量子力学的发展，而提出了海森堡不确定原理等限制，一别于古典物理，诸如位置与动量等无法同时精准测出其值；此外关于粒子位置等特性由机率密度描述所取代。一些物理学家例如爱因斯坦，认为量子力学并未完整地描述物理系统的状态，亦即质疑量子力学是不完备的。因此量子力学的背后应该隐藏了一个尚未发现的理论，可以完整解释物理系统所有可观测量的演化行为，而避免掉任何不确定性或随机性。

历史上爱因斯坦是隐变量理论的主要倡导者，出于对标准量子力学诠释的机率性解释的不满。他曾说：「我相信上帝不掷骰子。」

Historically, in physics, hidden variable theories were espoused by some physicists who argued that the state of a physical system, as formulated by quantum mechanics, does not give a complete description for the system; i.e., that quantum mechanics is ultimately incomplete, and that a complete theory would provide descriptive categories to account for all observable behavior and thus avoid any indeterminism. The existence of indeterminacy for some measurements is a characteristic of prevalent interpretations of quantum mechanics; moreover, bounds for indeterminacy can be expressed in a quantitative form by the Heisenberg uncertainty principle.