During intestinal inflammation, host processes known as nutritional immunity starve gut microbes of essential micronutrients such as iron. Enteric pathogens such as Salmonella overcome nutritional immunity using a series of exquisite mechanisms, including producing iron-chelating molecules termed siderophores. Although the host and pathogens compete for iron in the context of a vast number of gut commensals, how the commensal bacteria survive iron limitation, as well as the roles of commensal bacteria in this tug-of-war for iron remain largely unknown. We demonstrate that the model gut commensal Bacteroides thetaiotaomicron acquires iron by pirating siderophores from Salmonella, which induces intestinal iron limitation. B. thetaiotaomicron secretes a surface-exposed lipoprotein secreted into outer membrane vesicles to capture siderophores. Further, this siderophore acquisition mechanism can be exploited by Salmonella to “re-pirate” siderophores from gut commensals to evade nutritional immunity. As the host and pathogen have long been considered the only two essential facets of nutritional immunity, this work adds commensal iron metabolism as a previously unrecognized dimension to the intricate interactions between pathogen and nutritional immunity.