This Special Issue is associated with the European Conference on Integrated Optics (ECIO). The ECIO 2020 conference was held on June 23-24, 2020, and was initially scheduled in Paris, France. Due to the health and safety concerns related to the Covid-19 pandemic, the conference organizing committee has decided to adopt a digital conference format. The particularity of ECIO 2020 was to only have live talks in order to favor at maximum the interactions between speakers and attendees. This conference, organized by the Center for Nanoscience and Nanotechnology, Paris-Saclay University-CNRS, was the 22nd in a series that started in London in 1981. It attracted 640 participants from all over the world, with 103 oral presentations, including 2 plenary talks, 5 keynotes, 14 invited, 45 regular, and 57 poster speakers. The conference covered a diverse range of subjects in integrated optics and optoelectronics.