AI4Cities brings together the leading European cities in the intersection of ‘Smart Cities’ and Greenhouse Gas (GHG) emissions reduction, in order to speed up and steer the creation of new breakthrough solutions in how Artificial Intelligence (AI) can support cities’ strategic plans to become Carbon Neutral. Right now is the time to direct AI research/innovation towards the societal needs -- to assign detailed, pragmatic, solvable ‘missions’ from the cities’ climate action plans to AI developers. Through these missions, this project will create breakthrough, scalable, European solutions for these specific needs, and thus lead to immediate, concrete and measurable emissions savings, but more importantly, give examples on how to create impact and better future, for the whole of the AI community as well as all the European cities and citizens. On one hand, the opportunity window for European AI leadership is closing fast in the competition between solutions coming from the US and China - what kind of AI solutions govern us in the future is of great policy interest for Europe. On the other hand, urban emission reduction ambitions in most of the cities are set up so high that many of them are not realistically achievable without exploiting best-in-class ICT technologies. While cities are different, the largest opportunities for emission reduction in European cities are very similar. The highest common reduction targets in most cities’ climate action plans are in transport and in buildings’ energy use. As an example, in Helsinki, the production of Electricity and Heating accounts for 71% of GHG emissions; urban transportation and traffic account for 24%. Combined, these two sectors total 95% of Helsinki’s total carbon footprint. The purpose of this PCP is to support Cities’ transition to carbon neutrality, by applying the use of AI and related enabling digital technologies to tackle the challenge of reducing the Cities GHG emissions.