These are the Proceedings of the scientific activities of CORFU2023, the 23rd Hellenic School and Workshops on Elementary Particle Physics and Gravity, which took place from 23rd April to 6th May 2023 and from 27th August to 1st October, 2023. The Workshops were hosted by the European Institute for Sciences and their Applications (EISA) in the conference center of the former Royal Palace Garden of Mon Repos in Corfu, Greece. The CORFU2023 activities consisted of seven International Workshops and one Summer School, bringing together world class scientists and young researchers to interact and forge new collaborations.

Specifically, the CORFU2023 hosted the following sessions:
• Workshop on Future Accelerators, 23-29 April 2023
• Workshop on Theoretical Particle Cosmology in the Early and Late Universe, 30 April - 6 May 2023
• Workshop on the Standard Model and Beyond, 27 August - 7 September 2023
• George Fest 2023: Celebrating the Life and Work of George Zoupanos, 4 September 2023
• Workshop on Tensions in Cosmology, 6 – 13 September 2023
• Workshop on Quantum Gravity, Strings and the Swampland, 12-19 September 2023
• Workshop on Noncommutative and Generalized Geometry in String Theory, Gauge Theory and Related Physical Models, 18-25 September 2023
• KICC-Villum Summer School on Gravitational Waves, 24 September – 1 October 2023

All talks (slides and recorded videos can be found in the homepage of CORFU2023: