Entomopathogenic nematodes (EPNs) have been commercialized as biopesticides since the 1980s. Since the 1990s, research on the application, biology, and ecology of these biocontrol agents has seen exponential growth, and since the mid-2000s basic research on EPNs has further expanded due to the use of the nematodes and their symbiotic bacteria as tractable model systems for many basic biological and ecological questions. This chapter focuses on the use of EPNs as biopesticides in a wide range of agricultural and other commodities. However, it also provides overviews on EPN biology and ecology and mass production and application technology and interactions with other management tools as they are necessary for a better understanding of the strengths and limitations of EPNs as biopesticides.