同音异义语（Homophone），指一个词语的发音与另外一个词语相同，但意义却不同。这些词可能写法相同，以中文而言，例如「杜鹃」一词，可以指一种鸟类，也可以指杜鹃花；也可能写法不同，例如制服、制伏等等。写法相同的同音异义语同时也是同形异义语。在表音文本中，同音异义语也可以指与其他词组或字母发音相同的词组或字母。

英文词汇「Homophone」的字源是希腊文的「homo-」 (ὁμο-，相同)，以及「phōnḗ」 (φωνή，发声)。反义词为「heterophone」，即为多音字。

A homophone is a word that is pronounced the same as another word but differs in meaning, and may differ in spelling. The words may be spelled the same, such as rose (flower) and rose (past tense of "rise"), or differently, such as carat, caret, and carrot, or to, two, and too. Homophones that are spelled the same are also both homographs and homonyms. Homophones that are spelled differently are also called heterographs. The term "homophone" may also apply to units longer or shorter than words, such as phrases, letters or groups of letters that are pronounced the same as another phrase, letter or group of letters.