This book constitutes the proceedings of the 15th IFIP WG 8.5 International Conference on Electronic Participation, ePart 2023, held in Budapest, Hungary, in September 2023, in conjunction with the IFIP WG 8.5 Conference on Electronic Government (EGOV 2023) and the Conference for E-Democracy and Open Government Conference (CeDEM 2023). A total of 38 full papers has been carefully reviewed and selected from 106 submissions. Eight of the accepted papers are included in this book. They were organized in topical sections as follows: E-participation; digital transformation; digital technology; and digital sovereignty.