The International Symposium on Systems with Fast Ionic Transport (ISSFIT) is a biennial or triennial event which, since its first edition held in Slovakia, Smolenice in 1985, attracts scientists and researchers working in the field of solid electrolyte materials. The goal of each ISSFIT is to highlight the most recent developments in various aspects of charge transport in materials from the fundamental understanding to application. The 15th International Symposium on Systems with Fast Ionic Transport - ISSFIT-15 will pursue this goal by providing an attractive scientific and social programme for participants who will exchange recent progress and new knowledge in person - just like in the good old days. It is therefore our great pleasure to invite you to join us at f2f ISSFIT-15 from 18 to 22 April 2023 in Dubrovnik – the pearl of the Croatian Adriatic coast, and enjoy both a great conference and a pleasant and successful stay!