This book constitutes the refereed proceedings of the 23rd International Symposium on String Processing and Information Retrieval, SPIRE 2016, held in Beppu, Japan, in October 2016. The 25 full papers presented were carefully reviewed and selected from 46 submissions. The focus of the papers is on fundamental studies of string processes and information retrieval and its applications for example to areas such as bioinformatics, Web mining and others.