This volume presents peer-reviewed and selected papers from the 2024 European Conference on Integrated Optics (ECIO), held on 17-19 June, 2024, and organized by RWTH Aachen University, Germany, in collaboration with Max-Planck Institute of Microstructure Physics, Technical University of Berlin, Leibniz Institute for High Performance Microelectronics, and Karlsruhe Institute of Technology. In the 25th edition of this conference, internationally recognized experts share their latest research and showcase their products and services in the field of integrated optics, optoelectronics, and nano-photonics. The conference focuses on leading-edge research and its broad application scope ranges from tele/datacom, optical interconnects, and (bio) optical sensing to more disruptive areas such as quantum computing and programmable photonics.