控制理论是工程学与数学的跨领域分支，主要处理在有输入信号的动力系统的行为。系统的外部输入称为「参考值」，系统中的一个或多个变量需随着参考值变化，控制器处理系统的输入，使系统输出得到预期的效果。

控制理论一般的目的是借由控制器的动作让系统稳定，也就是系统维持在设置值，而且不会在设置值附近晃动。

连续系统一般会用微分方程来表示。若微分方程是线性常系数，可以将微分方程取拉普拉斯转换，将其输入和输出之间的关系用传递函数表示。若微分方程为非线性，已找到其解，可以将非线性方程在此解附近进行线性化。若所得的线性化微分方程是常系数的，也可以用拉普拉斯转换得到传递函数。

Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs, and how their behavior is modified by feedback. The usual objective of control theory is to control a system, often called the plant, so its output follows a desired control signal, called the reference, which may be a fixed or changing value. To do this a controller is designed, which monitors the output and compares it with the reference. The difference between actual and desired output, called the error signal, is applied as feedback to the input of the system, to bring the actual output closer to the reference. Some topics studied in control theory are stability (whether the output will converge to the reference value or oscillate about it), controllability and observability.