国际标准书号（英语：International Standard Book Number，缩写为ISBN），是国际通用的图书或独立的出版物（定期出版的期刊除外）代码。出版社可以通过国际标准书号清晰地辨认所有非期刊书籍。一个国际标准书号只有一个或一份相应的出版物与之对应。一本书的每一版或其他的变化，能够申请到一个新的国际标准书号。新版本如果在原来旧版的基础上没有内容上太大的变动，在出版时不会得到新的国际标准书号。当一本书同时有平装本与精装本出版时，平装本的国际标准书号不得用于精装本，反之亦然。

The International Standard Book Number (ISBN) is a unique numeric commercial book identifier.

An ISBN is assigned to each edition and variation (except reprintings) of a book. For example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, and 10 digits long if assigned before 2007. The method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country.