The proceedings of HEP 2023 - 40th Conference on Recent Developments in High Energy Physics and Cosmology invites scholars and experts in the fields of High Energy Physics, involved both in experimental and theoretical research, from various universities and institutions. The conference focuses on the more recent advancements in topics such as 'LHC experimental results', 'Astroparticle Physics', 'Cosmology', 'String Theory', 'Dark Matter' and others. The main goal of the conference is to present the related research work of the Greek scientific community, to promote the cooperation of experts and scholars in the field, to share the research achievements both on a national and international level. All accepted speakers were eligible to contribute to the Conference Proceedings on a voluntary basis.

The HEP2023 Conference is organized by the Hellenic Society for the Study of High Energy Physics and is hosted by the University of Ioannina (5-7 April 2023).