In recent decades, more than half the world’s people have become city dwellers. The expansion of towns and cities is termed urbanisation. Urbanisation is a process, comprised of three interrelated elements: (i) population growth—primarily people migrating from rural areas to urban areas; (ii) the physical transformation of non-urban areas into urban ones and; (iii) the concentration of economic and cultural activities in urban areas. Urban redevelopment and de-growth are processes related to urbanisation. Urbanisation substantially transforms physical environments, creating and exacerbating socially and spatially uneven environmental impacts. Negative environmental impacts (e.g., air pollution, soil contamination, natural hazards) are typically felt hardest by marginalised, vulnerable and disadvantaged populations. This phenomenon is called environmental injustice. Socially and spatially differentiated environmental benefits and harms in cities stem from deeply entrenched power relations that characterise land and property development, infrastructure provision and systems of urban governance. Inequities in service provision, facility-siting, accessibility and mobility can (re)produce unhealthy and/or hazardous urban environments. This chapter examines environmental injustices associated with the process of urbanisation, their manifestations, causes, consequences and potential remedies. Specific attention is given to how multiple axes of difference (re)produce socio-spatial inequalities. Key concepts are considered and illustrated via case examples from the developing and developed world.