八木天线也叫做“引向天线”、“八木宇田天线”（Yagi-Uda antenna）、“寄生天线”，是一种定向天线。这种天线是1928年由日本天线专家八木秀次和宇田新太郎两人设计的。

用于接收电视信号的所谓「鱼骨天线」其实也是八木天线的一种，因为这种天线往往使用了较多的引向器，所以看起来像是鱼骨而得名。

因为八木天线具有增益高、方向性强、结构简单的优点，它被广泛应用在无线电测向和长距离无线电通信。但是，若使用八木天线以收看模拟电视，容易受天气及地形环境所影响，导致电视画面出现雪花、残影等的现象。

A Yagi-Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of multiple parallel elements in a line, usually half-wave dipoles made of metal rods. Yagi-Uda antennas consist of a single driven element connected to the transmitter or receiver with a transmission line, and additional parasitic elements: a so-called reflector and one or more directors. It was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Japan, and (with a lesser role played by his colleague) Hidetsugu Yagi.