The IRIS project supports the Lighthouse cities of Utrecht (NL), Göteborg (SE) and Nice Côte d’Azur (FR) and their Follower cities Vaasa (FI), Alexandroupolis (GR), Santa Cruz de Tenerife (ES), and Focsani (RO) to address their urgent need to deliver energy and mobility services in their cities that are cheaper, better accessible, reliable, and that contribute to a better and more sustainable urban quality of life. By demonstrating smart solutions that integrate energy, mobility and ict, rooted in a City Innovation Platform, IRIS quantifies their value, and connects interests of many different stakeholders in innovative business models, allowing for upscale and replication of integrated solutions for sustainable cities across Europe and world-wide. To achieve this, IRIS works along five Transition Tracks based on common challenges, encompassing 16 integrated solutions that cities can mix and match according to their characteristics and district specific needs. Track 1, 2 and 3 enhance energy efficiency and utilize grid flexibility by balancing supply and demand dynamically and by 2nd life battery and V2G storage, to allow increase of renewable energy production and roll-out of e-cars and e-buses. Track 4 supports this by data sharing, a common architecture, use of standards, and governance practices accelerating innovation, standardisation and implementation of affordable smart applications. Track 5 integrates interdisciplinary citizen engagement and co-creation in Tracks 1 to 4, connecting the needs of end-users with those of other stakeholders, in further support of innovative business models. The expected impacts of IRIS are an open innovation ecosystem motivating citizens to act as prosumers; more effective urban planning and governance of integrated solutions; exploitation of validated innovative business models based on multi-stakeholder collaboration; more stable, secure and affordable energy and mobility services for citizens, with improved air quality.