耳机（又称耳筒、听筒、英文为Headphone），是一对转换单元，它接受媒体播放器或接收器所发出的电信号，利用贴近耳朵的扬声器将其转化成可以听到的音波。耳机一般是与媒体播放器可分离的，利用一个插头连接。好处是在不影响旁人的情况下，可独自聆听音响；亦可隔开周围环境的声响，对在录音室、DJ、旅途、运动等在噪吵环境下使用的人很有帮助。

耳机原是给电话和无线电上使用的，但随着可携式电子设备的盛行，耳机多用于手机、随身听、收音机。可携式电玩和数字音频播放器等。亦同时见用于电脑和Hi-fi音响之中。

Headphones (or head-phones in the early days of telephony and radio) are a pair of small listening devices that are designed to be worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound in the user's ear. Headphones are designed to allow a single user to listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air, for anyone nearby to hear. Headphones are also known as earspeakers, earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the speakers in place. The other type, known as earbuds or earphones consist of individual units that plug into the user's ear canal. In the context of telecommunication, a headset is a combination of headphone and microphone. Headphones either connect directly to a signal source such as an audio amplifier, radio, CD player, portable media player, mobile phone, video game consoles, electronic musical instrument, or use wireless technology such as bluetooth or FM radio. Early headphones were first used by radio pioneers (crystal sets) and also by radio telephone and telegraph operators allowing a better audio reception without disturbing others around. Initially the audio quality was mediocre and a step forward was the invention of high fidelity headphones.