he article starts by summarizing the state of the art of the current debate on scalar politics in the management of natural resources, in particular water. Against this background, we review the territorial, juridical and political evolution of basin organizations in the Iberian Peninsula, since their creation in 1926 to the situation in 2015, in the light of current critical approaches to the river basin as the unquestionable unit for water management. It is argued that when discussing ‘spatial fit’ issues in relation to the management of natural resources, special attention should be given to the changes in social relationships and power structures implied by different options, within their specific historical and geographical contexts. Key questions to be addressed include: when is the river basin an appropriate alternative for management decisions; what type of decisions are to be taken at the basin scale; and what sustainable practices and legitimate rights can be endangered.