© 2018 selection and editorial matter, Rob Kitchin, Tracey P. Lauriault and Gavin McArdle; individual chapters, the contributors. There is a rich history of data being generated about cities concerning their form, their citizens, the activities that take place, and their connections with other locales. These data have been generated in a plethora of different ways, including audits, cartographic surveying, interviews, questionnaires, observations, photography and remote sensing, and are quantitative and qualitative in nature, stored in ledgers, notebooks, albums, files, databases and other media. Data about cities provide a wealth of facts, figures, snapshots and opinions that can be converted into various forms of derived data, transposed into visualizations, such as graphs, maps and infographics, analysed statistically or discursively, and interpreted and turned into information and knowledge. As such, urban data form a key input for understanding city life, solving urban problems, formulating policy and plans, guiding operational governance, modelling possible futures and tackling a diverse set of other issues. For as long as data have been generated about cities then, various kinds of data-informed urbanism have been occurring.