The UN Ocean Decade–endorsed Digital Twins of the Ocean (DITTO) programme will convene its flagship global event, the 2026 DITTO Summit, in Japan. Building on the in-person summits in London (2022) and Xiamen (2023), as well as the online event in January 2026, the 2026 DITTO Summit in Japan brings together developers, scientists, operational agencies, policymakers, and industry leaders to advance the science, technology, and application of ocean digital twins. The Summit features plenary talks, thematic sessions, demonstrations, and networking, and highlights shared frameworks, interoperability, “what-if” scenario capabilities, and real-world applications that support ocean protection, effective governance, and a sustainable blue economy.