元音，又称元音，是音素的一种，与辅音相对。元音是在发音过程中由气流通过口腔而不受阻碍发出的音。

发元音时，气流从肺部通过声门冲击声带，使声带发出均匀震动，然后震音气流不受阻碍地通过口腔、鼻腔，通过舌、唇的调节而发出不同的声音。发元音时声带必然震动，这叫做浊音。也有的语言发元音时声带不振动，发出清元音（voiceless vowel）。

元音并非在所有的语言中都与元音字母一一对应，一些元音字母的组合也可以表示特殊的元音，比如汉语中的某些复韵母；某些语言中一些元音字母在某些情况下不发音，如法语中元音字母“e”在词末。

In phonetics, a vowel is a sound in spoken language, with two competing definitions. In the more common phonetic definition, a vowel is a sound pronounced with an open vocal tract, so that the tongue does not touch the lips, teeth, or roof of the mouth, such as the English "ah" /ɑː/ or "oh" /oʊ/. There is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as the English "sh" [ʃː], which have a constriction or closure at some point along the vocal tract. In the other, phonological definition, a vowel is defined as syllabic, the sound that forms the peak of a syllable. A phonetically equivalent but non-syllabic sound is a semivowel.