Non-alcoholic steatohepatitis (NASH) is a severe type of the non-alcoholic fatty liver disease (NAFLD). NASH is a growing global health concern due to its increasing morbidity, lack of well-defined biomarkers and lack of clinically effective treatments. Using metabolomic analysis, the most significantly changed active lipid sphingosine d18:1 [So(d18:1)] is selected from NASH patients. So(d18:1) inhibits macrophage HIF-2 alpha as a direct inhibitor and promotes the inflammatory factors secretion. Male macrophage-specific HIF-2 alpha knockout and overexpression mice verified the protective effect of HIF-2 alpha on NASH progression. Importantly, the HIF-2 alpha stabilizer FG-4592 alleviates liver inflammation and fibrosis in NASH, which indicated that macrophage HIF-2 alpha is a potential drug target for NASH treatment. Overall, this study confirms that So(d18:1) promotes NASH and clarifies that So(d18:1) inhibits the transcriptional activity of HIF-2 alpha in liver macrophages by suppressing the interaction of HIF-2 alpha with ARNT, suggesting that macrophage HIF-2 alpha may be a potential target for the treatment of NASH. Non-alcoholic steatohepatitis has with few well-defined biomarkers or clinically effective treatments but is promoted by inflammation. Here, the authors find an active lipid [So(d18:1)] that is significantly changed in patients and promotes inflammation by directly inhibiting macrophage HIF-2 alpha.