1 INTRODUCTION The development of Smart Sustainable Cities is at the heart of our pursuit of sustainability. Modern cities are responsible for 80 per cent of global economic output and 70 per cent of global energy consumption and GHG emissions, and, by year 2050, cities will be home to 66 per cent of the world’s projected 9 billion inhabitants. The ITU-T Focus Group on Smart Sustainable Cities was established as an open platform for smart-city stakeholders – such as municipalities; academic and research institutes; non-governmental organizations (NGOs); and ICT organizations, industry forums and consortia – to exchange knowledge in the interests of identifying the standardized frameworks needed to support the integration of ICT services in smart cities.ITU collaboration with UN Economic Commission for Europe (UNECE), within the framework provided by the ITU-T Focus Group on Smart Sustainable Cities, led to the international agreement of a definition of Smart Sustainable Cities: “A smart sustainable city (SSC) is an innovative city that uses information and communication technologies (ICTs) and other means to improve quality of life, eficiency of urban operation and services, and competitiveness, while ensuring that it meets the needs of present and future generations with respect to economic, social, environmental as well as cultural aspects”. This compendium of the 21 Technical Reports and Specifications developed by the Focus Group provides an overview of how ICTs could be deployed with traditional infrastructures to promote the coordinated, integrated use of new digital technologies in meeting 21st Century urban-development objectives. In September 2015, the United Nations General Assembly achieved consensus on a new set of 17 Sustainable Development Goals, adopting a global sustainable development agenda, applicable to both developed and developing countries. ICTs play an important role in this agenda, in particular as part of Goal 9 – Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation – which includes a target to increase access to ICTs and provide universal and afordable access to the Internet. Addressing urban development more directly, Goal 11 – Make cities and human setlements inclusive, safe, resilient ITU-T’s Technical Reports and Specifications 1