This chapter provides a reflective critique of Mobility as a Service (MaaS), an emerging development seeking a role within the Smart Mobility paradigm. We assess a range of its future implications for urban policymakers in terms of governance and sustainability (i.e., social and environmental impacts). We begin by describing the origins of the MaaS concept, along with the features of precursor technologies and current early examples. We then reflect on the marketing of MaaS and use it to consider how we might anticipate some potentially less desirable aspects of the promoted business models. Finally, we discuss the implications for governance.