This book constitutes the proceedings of the 15th International Conference on Research Challenges in Information Sciences, RCIS 2021, which was planned to take place in Limassol, Cyprus, but had to change to an online event due to the COVID-19 pandemic. The conference took place virtually during May 11-14, 2021. It focused on the special theme "Information Science and Global Crisis". The scope of RCIS is summarized by the thematic areas of information systems and their engineering; user-oriented approaches; data and information management; business process management; domain-specific information systems engineering; data science; information infrastructures, and reflective research and practice. The 29 full papers and 6 work-in-progress papers presented in this volume were carefully reviewed and selected from 99 submissions. They were organized in topical sections named: Business and Industrial Processes, Information Security and Risk Management, Data and Information Management, Domain-specific Information Systems Engineering, User-Centered Approaches, Data Science and Decision Support, and Information Systems and Their Engineering. The volume also contains 13 poster and demo papers, and 4 doctoral consortium papers. In addition, two-page summaries of tutorials and research project papers can be found in the back matter.