北约音标字母（英语：NATO phonetic alphabet），正式称为国际无线电通话拼写字母（英语：International radiotelephony spelling alphabet），是最常使用的拼写字母。虽常称作「语音字母」（phonetic alphabets），但其字母拼法与语音系统（比如国际音标）并没有关连。因罗马字母之发音在各国念法常有差异（如字母Y在德文发音念为ypsilon），北约音标字母中的A到Z（共26个拉丁字母）和0到9（共10个印度阿拉伯数字）使用截头表音（如Alfa代表 A、Bravo代表 B，等等）。由此，无论透过无线电或电话收发语音频息双方之母语是否相同，众多字母与数字组成的关键配搭也可较为准确地朗读及知悉，并确保发送之语音有一定的可理解性，这在保证航行或涉及人员安全的时候尤为重要。

The International Radiotelephony Spelling Alphabet, commonly known as the NATO phonetic alphabet and also known as the ICAO radiotelephonic, phonetic or spelling alphabet and the ITU radiotelephonic or phonetic alphabet, is the most widely used radiotelephonic spelling alphabet. Although often called "phonetic alphabets", spelling alphabets are not associated with phonetic transcription systems such as the International Phonetic Alphabet. Instead, the International Civil Aviation Organization (ICAO) alphabet assigned codewords acrophonically to the letters of the English alphabet, so that critical combinations of letters and numbers can be pronounced and understood by those who exchange voice messages by radio or telephone regardless of language barriers or the quality of the communication channel.