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) used to pronounce a single phoneme. For example, [pʰ] (as in pin) and [p] (as in spin) are allophones for the phoneme /p/ in the English language. Although a phoneme's allophones are all alternative pronunciations for a phoneme, the specific allophone selected in a given situation is often predictable. Changing the allophone used by native speakers for a given phoneme in a specific context usually will not change the meaning of a word but the result may sound non-native or unintelligible. Native speakers of a given language usually perceive one phoneme in their language as a single distinctive sound in that language and are "both unaware of and even shocked by" the allophone variations used to pronounce single phonemes.

Every time a speech sound is produced for a given phoneme, it will be slightly different from other utterances, even for the same speaker. This has led to some debate over how real, and how universal, phonemes really are (see phoneme for details). Only some of the variation is significant (i.e., detectable or perceivable) to speakers. There are two types of allophones, based on whether a phoneme must be pronounced using a specific allophone in a specific situation, or whether the speaker has freedom to (unconsciously) choose which allophone he or she will use.