Our engagement with this ICMI Study Conference began when we accepted invitations from the ICMI President, Frederick Leung, to co-chair the Study 26: Advances in Geometry Education. Although we have both worked internationally in geometry education for decades, we had not previously met one another. A briefing meeting with the President, and the Secretary General, Jean-Luc Dorier, provided context and scope for the Study. As with all ICMI studies, the central aims are to consider the topic (in our case geometry education) with respect to theory, research, practice, and policy; and to suggest new directions of research that take into account contextual, cultural, national, and political dimensions of the field. We then worked collaboratively with Professors Leung, Dorier, and other members of the ICMI Executive, to establish an International Program Committee (IPC) with expertise in geometry education. The IPC members have invested substantial time and effort to be part of the IPC, over an extended period. We are grateful for their collective wisdom and technical expertise in framing the core work of the Study. We are especially appreciative of Professor Fabien Emprin’s commitment to the Study by taking on the responsibility of Conference Convenor. Fabien’s leadership and organisational skills became on integral part of the Study’s success. We would also like to acknowledge the effort that some participants from economically disadvantaged countries have made to attend the conference, and the economic support we have received from ICMI and Trent University (Canada) to support their attendance. The IPC met in Valencia in February 2023 to develop the ICMI Study 26 Discussion Document, included at the end of the Proceedings, which was finalized and distributed internationally in June 2023. We express our gratitude to the University of Valencia for providing working spaces and facilities during the three-day meeting. The Study Document served as a call for papers for the ICMI Study 26 Conference, hosted by the Université de Reims Champagne Ardenne, France, during April, 2024. An ICMI Study Conference is quite different to a traditional conference. A majority of the time is devoted to the engagement of Working Groups organized around the topics and led by IPC members. During these Working Groups brief presentations by the participants, based on their papers, serve as a catalyst for in-depth exploration of the topics and sub-topics —with the primary purpose being the preparation and initial development of a published volume. The activity of the Study is organized around four focused topics, aimed to provide complementary perspectives and approaches to the teaching and learning of geometry. Contributions to the topics were organized around sets of related sub-topics, each sub-topic focusing on a specific issue and stating a set of questions aimed to lead discussions, as defined in the Discussion Document. The four topics are: A. Theoretical perspectives; B. Curricular and methodological approaches; C. Resources for teaching and learning geometry; and D. Multidisciplinary perspectives. These topics and related sub-topics provided the basis for inviting papers. Each submission was reviewed by at least two IPC members, and authors of accepted papers were invited to participate in the Study Conference. Accepted papers were then revised (when necessary) by the authors, before being published in these electronic conference proceedings. The conference proceedings include 60 papers from around the world. The countries represented in the Proceedings include: Argentina, Australia, Brazil, Canada, Chile, China, Colombia, Costa Rica, Croatia, France, Germany, Greece, Hong Kong, India, Iran, Israel, Italy, Japan, Malawi, Mexico, New Zealand, Portugal, Serbia, South Africa, Spain, Sweden, Switzerland, United Kingdom, and the United States. In addition, we invited two esteemed scholars to present plenary lectures and another five to participate in a plenary panel on geometry practices within diverse cultural settings. To ensure that teachers’ voices were well-represented at the Study Conference, we invited several practitioners actively involved in collaborative geometry projects to participate in a plenary panel that focused on French perspectives of teaching geometry. We would like to thank the Local Organizing Committee members and their support staff and students of the l’IREM de Reims at the Université de Reims Champagne-Ardenne for all their work in hosting a successful ICMI Study 26 Conference. Preparation of the ICMI Study 26 volume, begun during the Study Conference, will continue in four virtual collaborative groups, during 2024-25. We aim for the Study Volume to be published in 2026 by Springer Nature in the New ICMI Studies Series. An ICMI Study requires sustained commitment on three major projects (the Discussion Document, Study Conference and Study Volume) throughout its focused program of work. Along with the unwavering support and guidance we have received from Frederick Leung and Jean-Luc Dorier, we would like to acknowledge the help we have received from Merrilyn Goos (Vice President of ICMI), and Lena Koch (IMU Secretariat) at critical times during the development of the work program.