效果器，或称作踏板，是一种可以令电子乐器或音频的音色加以修饰的电子器材。音乐人会在现场表演或是在录音室时使用效果器，一般常用在电吉他、电子琴、电钢琴或电贝斯。大多数的效果器被使用在电子乐器，然而也有少量设计用在原声乐器、鼓与声乐。一般效果器的例子为哇哇踏板、模糊破音、以及残响效果器。

效果器的格式有内置在吉他音箱的、封装在桌上式的、单颗效果器，以及机架式效果器，甚至也有内置在乐器上面的类型。单颗效果器是一个小型的金属或塑胶盒，放置在乐手面前的地板上，并用插线电线（Patch cord，即导线）连接乐器与乐器放大器。它由一个或多个脚控切换开关来控制，而上面则有旋钮控制音量、音调与效果的强度，通常仅提供一至两个效果。设备在19吋机架的机架式效果器通常包含数种效果。

An effects unit or pedal is an electronic device that alters how a musical instrument or other audio source sounds. Some effects subtly "color" a sound while others transform it dramatically. Musicians use effects units during live performances or in the studio, typically with electric guitar, electronic keyboard, electric piano or electric bass. While most frequently used with electric or electronic instruments, effects can also be used with acoustic instruments, drums and vocals. Examples of common effects units include wah-wah pedals, fuzzboxes and reverb units.