This gold open access book gathers the proceedings of the ReSBE Conference, ReShaping the Built Environment through Sustainability and Circularity, held in Thessaloniki, Greece, on October 20-23, 2026. It explores transformative pathways towards a regenerative, resilient, and circular built environment, addressing current challenges and emerging approaches across buildings, infrastructures, cities, and regions. This book presents new models, methodologies, technologies, case studies, and decision-support approaches aimed at accelerating the transition toward sustainability and circularity in the built environment. This book covers a broad range of topics, including circular design and construction, sustainability assessment frameworks, lifecycle assessment and monitoring, digitalization and automation, climate adaptation and resilience, energy and carbon performance, innovative and bio-based materials, urban and regional circularity, governance and policy frameworks, financing mechanisms, stakeholder collaboration models, and societal and educational dimensions of sustainable transitions.