Introducing this special issue on public transport as public space, we discuss challenges in approaching public transport as public space and outline how incorporating approaches from different disciplines associated with urban studies is essential for this ambition. We offer an account of the multi-dimensional aspects of public transport as public space, including concepts of public space, questions of encounters and conviviality, linkages between micro- and macro-practices, regulations, discrepancies, conflicts and associated negative encounters, historicised experiences and political perspectives. We stress the need to expand existing perspectives on public space by embracing mobile spaces such as public transport. This entails scrutinising spaces inside public transport vehicles and stations as well as analysing the various ways across the sometimes physical and sometimes invisible barriers defined in written rules, separating public transport space from the remainder of the city’s public spaces, notably that of the street. Thus, the special issue: explores questions about the spatiality of publicness; attends to public space as a normative ideal; considers critical aspects of passengering as related to conviviality and contested encounters; and, addresses how the publicness of public transport is affected by modernisation, post-colonialism and urban politics. As we strongly feel that these questions require learning from across disciplines, the special issue includes contributions from diverse fields across the realm of urban studies and humanities alike.