Disease ecology and conservation biology are two disciplines that, despite their apparent differences, are directly relevant to each other. Biological diversity—the focus of the discipline of conservation biology—is unequivocally affected by the presence of parasites and pathogenic organisms. For example, an increasing number of taxa are being endangered by emerging diseases—the first section of this chapter discusses the various ways in which this endangerment takes place. Conversely, mounting evidence suggests that high levels of species diversity protect natural communities against devastating epidemics. At the same time, parasitic organisms themselves constitute a significant component, and perhaps the majority, of the world’s biological richness. Similar to the rest of the planet’s biodiversity, they are increasingly endangered by human activities. As our understanding of the role that parasites play in the working of natural ecosystems has grown, so has the realization that their disappearance can have wide-ranging implications for ecosystem function. The last section of this chapter focuses on the new subdiscipline of parasite conservation, detailing first the present understanding of the important ecosystem services provided by parasites and pathogens, and second the processes through which parasitic organisms are becoming endangered.