This is a comprehensive introduction to the career and contributions of the compiler of the first of the ‘four books’, the four great collections of Twelver Shī‘ī ḥadīṯ completed before the Saljuk conquest of Baghdad in 1055. The article is divided into four sections. The authors first review the problems with source materials on al-Kulaynī. Section two first discusses the times in which al-Kulaynī lived, noting the progressive decline of Abbasid power and the rise of numerous semi-autonomou...