Income inequality is increasing in European cities and this rising inequality has a spatial footprint in cities and neighbourhoods. Poor and rich people are increasingly living separated and this can threaten the social sustainability of cities. Low income people, often with an ethnic minority background, can get cut off from important social networks and mainstream society, and this can lead to social unrest. Increasing inequality and socio-economic segregation is therefore a major concern for local and national governments. Socio-economic segregation is the outcome of a combination of inequality and poverty, and the spatial organisation of urban housing markets. Poverty, and living in poverty concentration neighbourhoods is transmitted between generations and neighbourhood poverty is reproduced over time through to the residential mobility behaviour of households. Urban policy often focusses on reducing segregation through physical measures in cities, such as demolishing houses in deprived neighbourhoods and replacing them with housing for the middle classes. Such policies will not solve the underlying causes of segregation, but only redistribute poverty over cities. Policy initiatives should first of all focus on reducing inequality by creating equal opportunities for people and invest in education and training. Inclusive growth strategies should combine both people-based and area-based policy measures.