Italian social science research has historically been hindered by fragmented research infrastructure and a critical lack of longitudinal data, with profound consequences for understanding and addressing social change. The Italian Online Probability Panel (IOPP) will be the first initiative in Italy to produce high-quality longitudinal survey data monitoring social transformations. Launched in early 2025, IOPP is based on a probability sample of approximately 10,000 individuals aged 18–74, drawn from the national population register. Spanning five annual survey waves, it will gather longitudinal data via a core questionnaire, measuring enduring constructs such as family and housing, health, education, work, income, leisure, social integration and political attitudes, supplemented by one-time or rotating modules developed via open calls to the research community. Notably, IOPP has been developed within the FOSSR project, which addresses Italy’s infrastructural gap by establishing an innovative Research Data Infrastructure aligned with the European Open Science Cloud. It also connects IOPP with leading Research Data Infrastructures, such as CESSDA ERIC, SHARE ERIC, and RISIS, and international surveys like GUIDE and GGS, included in the ESFRI Roadmap 2021. IOPP thus represents a crucial step in embedding Italy within the global ecosystem of social science research.