SummaryInflammatory disorders are major health issues in which immune function and metabolic homeostasis are concertedly altered. Yet, the molecular mechanisms coordinating innate and metabolic pathways in homeostatic conditions are poorly understood. Here, we unveil a negative regulatory feedback loop involving the Stimulator of interferon genes (Sting) and the Fatty acid desaturase 2 (Fads2). At steady state, Sting regulates FA metabolism by repressing the activity of the Fads2 enzyme responsible for the desaturation of polyunsaturated FAs (PUFAs). Importantly, Sting activation increased Fads2 activity, while antagonizing Fads2 enhanced Sting activation, promoting the establishment of an anti-viral state. Remarkably, the cross-regulation between Sting and Fads2 is mediated by the cyclic GMP-AMP (cGAMP) Sting agonist and PUFAs. Indeed, we found that PUFAs inhibit Sting activation, while Sting agonists bind Fads2. Thus, our study identifies Sting as a master regulator of FA metabolism, and PUFAs as modulators of Sting-dependent inflammation. The interplay between Fads2 and Sting determines the fine-tuning of inflammatory responses, but comes at the expense of metabolic alterations, which are critical to consider in human pathologies associated with aberrant Sting activation.