For several years now, both eHealth applications and digitalization have been seen as fundamental to the new era of health informatics and public health. The current pandemic situation has also highlighted the importance of medical informatics for the scientific process of evidence-based reasoning and decision making at all levels of healthcare. This book presents the accepted full papers, short papers, and poster papers delivered as part of the 31st Medical Informatics in Europe Conference (MIE 2021), held virtually from 29-31 May 2021. MIE 2021 was originally due to be held in Athens, Greece, but due to the continuing pandemic situation, the conference was held as a virtual event. The 261 papers included here are grouped into 7 chapters: biomedical data, tools and methods; supporting care delivery; health and prevention; precision medicine and public health; human factors and citizen centered digital health; ethics, legal and societal aspects; and posters. Providing a state-of-the-art overview of medical informatics from around the world, the book will be of interest to all those working with eHealth applications and digitalization to improve the delivery of healthcare today.