同位异音（allophone）是语言学术语，指的是一个音位可以表示多于一个音。又称为同位音、音位变体。

例如英语中，/t/ 可以用来表示“top”中送气的[tʰ]或者“stop”中不送气的[t]，这样[tʰ]和[t]在英语中就是同位音，它们的共同音位是 /t/。

又如普通话中/ɤ/可以用来表示“德”的韵母[ɤ]，又可以表示感叹词“呢”的韵母[ə]，这样[ɤ]和[ə]在普通话中就是同位音，它们的共同音位是 /ɤ/。

声调语言的同位异音有时称为同位异调（allotone），比如在中文里的轻声调（neutral tone）。

In phonology, an allophone (/ˈæləfoʊn/; from the Greek:ἄλλος, állos, "other" and φωνή, phōnē, "voice, sound") is one of a set of multiple possible spoken sounds (or phones) or signs used to pronounce a single phoneme in a particular language. For example, [pʰ] (as in pin) and [p] (as in spin) are allophones for the phoneme /p/ in the English language. The specific allophone selected in a given situation is often predictable from the phonetic context (such allophones are called positional variants), but sometimes allophones occur in free variation. Replacing a sound by another allophone of the same phoneme will usually not change the meaning of a word, although sometimes the result may sound non-native or even unintelligible. Native speakers of a given language usually perceive one phoneme in that language as a single distinctive sound, and are "both unaware of and even shocked by" the allophone variations used to pronounce single phonemes.