A neutral vowel is an unstressed vowel sound, for example the /io/ in nation or the /a/ in orange. In phonetics, the neutral vowel is defined as a mid-central unrounded monophthong, i.e., a vowel phoneme formed with the tongue in the rest position, with lips unrounded.

The neutral vowel is usually represented in pronunciation guides like the International Phonetic Alphabet by the schwa symbol: ə.