Even with reperfusion therapy, ischemia-reperfusion (I/R) injury remains to be a major driver of organ failure associated with myocardial infarction, stroke, and liver transplantation, with effective therapeutic targets still elusive. Using in vitro hypoxia/reoxygenation (H/R) models, we discovered that the pharmacological inhibition of 15-lipoxygenase (ALOX15) by thiolox effectively mitigates myocardial I/R injury. While ALOX15—a well-established promoter of lipid peroxidation and ferroptosis—has been extensively studied in cardiac I/R, its involvement in multi-organ I/R injury and non-ferroptotic cell death has not been thoroughly investigated. To address this, we employed I/R models in three vital organs and found that either global deletion of Alox15 or its specific loss in hematopoietic cells (Alox15 ^ΔH ) consistently led to a reduction in infarct volume and improvement in function across the heart, brain, and liver. Mechanistically, this protection arose from the inhibition of pyroptosis. The underlying cascade involves mitochondrial reactive oxygen species (ROS) activating ALOX15 during reperfusion, which produces 15-HpETE, leading to a collapse of mitochondrial membrane potential (ΔΨm) and subsequent IP3R-mediated calcium (Ca²⁺) efflux. This Ca²⁺ surge initiates the assembly of NLRP3 inflammasome, driving GSDMD-dependent pyroptosis. Thus, ALOX15 acts as a keystone regulator bridging oxidative stress to pyroptosis via a mitochondria-Ca²⁺-pyroptosis axis. This axis functions independently of the organ type and is transmitted through both parenchymal and hematopoietic cells, suggesting that thiolox and targeted ALOX15 inhibition could be viable strategies for protecting multiple organs from I/R injury.