DT4GS is aimed at delivering an "Open Digital Twin Framework" for both shipping companies and the broader waterborne industry actors to tap into new opportunities made available through the use of Digital Twins (DTs). The project will enable shipping stakeholders to embrace the full spectrum of DT innovations to support smart green shipping in the upgrade of existing ships and new vessels. DT4GS will cover the full ship lifecycle by embracing federation of DT applications as well as utilising DTLF policies and related shared-dataspace developments for the sector. DT4GS applications will focus on shipping companies but will also provide decarbonisation decision support system for shipyards, equipment manufacturers, port authorities and operators, river commissions, classification societies, energy companies and transport/corridor infrastructure companies. DT4GS's objectives are to: 1. Support shipping companies in achieving up to 20% reduction in CO2e with a 2026 horizon, by developing and deploying real-time configurable DTs for ship and fleet operational performance optimisation in 4 Living Labs involving shipping companies, with different vessel types, and establishing fully validated industry services for Green Shipping Operational Optimisation DTs expected to be adopted by 1000+ ships by 2030. 2. Establish a comprehensive zero-emission shipping methodology and support Virtual Testbed and Decision Support Systems that address both new builds and retrofits comprising: a. A DT4GS (Green Shipping) Dataspace for the broader shipping sector contributing to GAIA-X by establishing a core European industry resource that accelerates the green and digital transition of waterborne shipping and transport value chains. b. Simulation based solutions to retrofit ships, targeting 55% reduced CO2e reduction by 2030. c. A smart green "new-build" reference design per vessel type. d. Virtual Testbed services for reducing the cost of physical testing of GS solutions by 20%.