EuCNC 2021 is the 30th edition of a successful series of a conference in the field of telecommunications, sponsored by the IEEE Communications Society (ComSoc) and the European Association for Signal Processing (EURASIP), and supported by the European Commission. The conference focuses on various aspects of 6G communications systems and networks, including cloud and virtualization solutions, management technologies, experimentation and testbeds, and applications and services. It targets to bring together researchers from all over the world to present the latest research results, and it is one of the main venues for demonstrating the results of research projects, especially from R&D programmes co-financed by the European Commission.