The ITU-T Study Group 20 (SG20), entitled “Internet of Things, digital twins and smart sustainable cities and communities (SSC&C)”, is responsible for the development of international standards that enable the deployment and evolution of IoT-based systems and smart sustainable environments. For the 2025–2028 study period, SG20 has been entrusted with a broad and forward-looking mandate covering technical, architectural, data-related and societal aspects of digital transformation. SG20 addresses the standardization of IoT and SSC&C from an end-to-end perspective, encompassing systems, applications, platforms and services. Its work contributes directly to enabling interoperability, scalability and sustainability across diverse vertical sectors and deployment scenarios, including urban and rural environments. In this context, Study Group 20 plays a key role in supporting Member States, industry, academia and other stakeholders in the adoption of digital technologies aligned with sustainable development objectives.