This paper discusses the limitations in the income-based poverty lines that are widely used to define poverty and to measure urban poverty in Africa, Asia and Latin America. This includes a discussion of whether the poverty lines defined by international agencies and national governments are set at levels that are realistic in relation to the costs of living in the larger/more prosperous/more expensive cities and the prices that the urban poor have to pay for essential non-food items. It also includes a discussion of what poverty definitions based only on income fail to take account of in regard to identifying deprivation and to helping inform poverty reduction policies and practices. This paper assembles data from many empirical studies which suggest that the scale and depth of urban poverty is systematically under-estimated in most of the official statistics produced or used by governments and international agencies.