This book reflects on what it means to live as urban citizens in a world increasingly shaped by the business and organisational logics of digital platforms. Where smart city strategies promote the roll-out of internet of things (IoT) technologies and big data analytics by city governments worldwide, platform urbanism responds to the deep and pervasive entanglements that exist between urban citizens, city services and platform ecosystems today. Recent years have witnessed a backlash against major global platforms, evidenced by burgeoning literatures on platform capitalism, the platform society, platform surveillance and platform governance, as well as regulatory attention towards the market power of platforms in their dominance of global data infrastructure. This book responds to these developments and asks: How do platform ecosystems reshape connected cities? How do urban researchers and policy makers respond to the logics of platform ecosystems and platform intermediation? What sorts of multisensory urban engagements are rendered through platform interfaces and modalities? And what sorts of governance challenges and responses are needed to cultivate and champion the digital public spaces of our connected lives.