This book constitutes the refereed proceedings of the 21st International Conference on Innovations for Community Services, I4CS 2021, held in Bamberg, Germany, in May 2021 as a hybrid event. The 14 full papers and 2 short papers presented in this volume were carefully reviewed and selected from 43 submissions. One short invited paper is also included. The papers focus on topics such as services for critical infrastructure; network architecture for communities; applications and services supporting work and life; community data and visualization; technology empowers industry processes; and future community support.