频分多路复用（Frequency-division multiplexing，FDM），也叫分频多任务，是一种将多路基带信号调制到不同频率载波上再进行叠加形成一个复合信号的多路复用技术。

历史上，电话网络曾使用FDM技术在单个物理电路上传输若干条语音信道。这样，12路语音信道被调制到载波上各自占据4KHz带宽。这路占据60－108KHz频段的复合信号被认为是一个组。反过来，五个这样的信号组本身被同样的方法多路复用到一个超级组中，这个组包含60条语音信道。进一步甚至有更高层次的多路复用，这样使得单个电路中传输几千条语音信道成为可能。

In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency sub-bands, each of which is used to carry a separate signal. This allows a single transmission medium such as the radio spectrum, a cable or optical fiber to be shared by multiple independent signals. Another use is to carry separate serial bits or segments of a higher rate signal in parallel.