Acute on chronic liver failure (ACLF) presents a significant clinical challenge, characterised by systemic inflammation, immune dysregulation and multiple organ failure. The Autotaxin (ATX)/ lysophosphatidic acid (LPA) axis has emerged as a significant contributor to ACLF pathogenesis. Quantification of LPA species holds promise as a diagnostic biomarker for ACLF, yet the role of individual LPA species remains understudied. This study addressed this gap by developing a novel high-throughput UHPLC-MS/MS method to quantify individual LPA species in plasma and tissue, paired with a targeted lipidomic assay to detect additional lipids, enhancing understanding of both LPA species and the broader lipidomic landscape in ACLF. The method was applied to characterise the individual LPA species in patients with cirrhosis, alcoholic hepatitis, and ACLF, comparing them with healthy controls. Elevated levels of both LPA 16:1 and LPA 18:1 were observed across all disease groups, with LPA 20:4 increasing in cirrhosis and ACLF, and LPA 22:6 specifically increasing in ACLF. These changes suggest potential roles for these LPA species as prognostic markers, with correlation analysis indicating associations between LPA 18:1 and immune mediators such as PDL-1. The study also demonstrated that inhibition of ATX in an ACLF mouse model led to distinct changes in LPA species and gene expression patterns, highlighting the therapeutic potential of targeting the ATX/LPA axis. These differential alterations in LPA species and lipidomic profiles provide insight into the mechanistic relationship between the ATX/LPA axis and ACLF pathophysiology. Lipidomic and transcriptomic analyses of immune cells underscored the role of immunometabolism in ACLF, suggesting that modulating immune cell metabolism could reduce inflammation and improve patient outcomes in ACLF. Overall, these findings support the hypothesis that elevated LPA species contribute to metabolic and immune dysregulation in ACLF and provide a foundation for further therapeutic exploration of the ATX-LPA axis.