环路增益（loop gain）为电子学及控制工程的名词，是指一反馈回路中的总增益，一般会以比例或是分贝表示。环路增益常用在放大器及电子振荡器的线路中，后来更扩展到控制工厂及设备的工业控制系统中。环路增益的概念也用在生物学中。在反馈回路中，为了控制输出，会量测设备、进程的输出，采样后，再以此影响输入信号，使输出控制的更理想。环路增益和环路相位移决定了设备的特性，也决定输出是否稳定，或是不稳定（振荡）。海因里希·巴克豪森在1921年最早发现环路增益在电子反馈放大器特性分析中的重要性，后来在1930年代由贝尔实验室的亨德里克·韦德·波德及哈里·奈奎斯特继续发展。

In electronics and control system theory, loop gain is the sum of the gain, expressed as a ratio or in decibels, around a feedback loop. Feedback loops are widely used in electronics in amplifiers and oscillators, and more generally in both electronic and nonelectronic industrial control systems to control industrial plant and equipment. The concept is also used in biology. In a feedback loop, the output of a device, process or plant is sampled and applied to alter the input, to better control the output. The loop gain, along with the related concept of loop phase shift, determines the behavior of the device, and particularly whether the output is stable, or unstable, which can result in oscillation. The importance of loop gain as a parameter for characterizing electronic feedback amplifiers was first recognized by Heinrich Barkhausen in 1921,was developed further by Hendrik Wade Bode and Harry Nyquist at Bell Labs in the 1930s.