行波管（TWT）是一种利用电子流与沿慢波系统行进的电磁波间的连续相互作用而放大超高频（微波）电磁波的电子管。

主要由电子枪、慢波系统和收集极等部分组成，常用的慢波系统是一螺旋线和梳形结构等，特点是工作频带宽，噪声低，适宜于作为中、小功率的放大器。电磁波行进方向与电子流方向相反的一种行波管，称为返波管，可用作一种频带很宽的微波振荡器。

A traveling-wave tube (TWT) is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs to a category of "linear beam" tubes, such as the klystron, in which the radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube. Although there are various types of TWT, two major categories are: