This book  contains extended, revised and selected papers from the 23rd International Conference on Enterprise Information Systems, ICEIS 2021, held online during April 2021. The 26 papers presented in this volume were carefully reviewed and selected for inclusion from a total of 241 submissions. They are grouped in sections on databases and information systems integration, artificial intelligence and decision support systems, information systems analysis and specification, software agents and internet computing, human-computer interaction, and enterprise architecture.