Bioregionalism is often presented as the politics of deep ecology, or deep ecology's social philosophy. That the ties uniting these doctrines are rarely explored can be put down to a perception amongst commentators that such links are self-evident and therefore unworthy of closer examination. By arguing that the bonds between deep ecology and bioregionalism are more tenuous than has often been assumed, this paper addresses this theoretical lacuna. There is nothing exclusive to the central tenets of deep ecology which provides us with a coherent rationale for a specifically bioregional form of decentralisation. However, deep ecology has nonetheless had an appreciable impact on bioregional thinking. In this context it is argued that bioregionalism's assimilation of aspects of deep ecology, and particularly an emphasis upon cross-species identification, undermines the project in various ways.