Obesity exacerbates renal injury following lower limb ischaemia-reperfusion (LLIRI) through mechanisms involving calcium dysregulation and oxidative-inflammatory-apoptotic cascades. However, the underlying pathways remain to be identified. Thus, this study aimed to elucidate the underlying pathways by using transcriptomics, multi-omics, and pharmacological validation. Utilizing transcriptomics, multi-omics analysis, and targeted biochemical/molecular assays in a high-fat diet-induced obese mouse model of LLIRI, combined with pharmacological validation using nicardipine in human renal tubular cells exposed to oxidative stress, we elucidated the underlying pathways linking calcium dysregulation to renal injury. In high-fat diet-induced obese mice, LLIRI triggered profound renal transcriptomic reprogramming, with 1530 differentially expressed genes significantly enriched in calcium homeostasis disruption (GO:0055074), NF-κB signalling (KEGG:mmu04064), and apoptosis. Mechanistically, LLIRI-induced surge in reactive oxygen species promoted renal calcium influx by downregulating calcium efflux transporters Atp2b4 (PMCA4) and Kcnma1 (BK channel), which led to Ca2+ overload. This results in activation of the transcription hub JUN, which orchestrated a triad of injury: oxidative stress, as evidenced by Nox4 upregulation and ATP/NAD+ depletion, which elevated lipid (MDA↑), protein (carbonyls↑), and DNA (8-OHdG↑, γ-H2AX↑) damage; inflammation, as evidenced by tumour necrosis factor-α/interleukin (IL)-1β/IL-18 elevation and macrophage infiltration (F4/80+/HMGB1+); and apoptosis, as evidenced by PUMA (Bbc3) induction, caspase-3/8 activation, and Bax/Bcl-2 imbalance. In vitro, H2O2-induced oxidative stress in human renal tubules replicated Ca2+ overload and JUN-driven apoptosis/senescence. Treatment with the L-type calcium channel blocker nicardipine (2.5 μM) attenuated calcium influx, suppressed JUN/Nox4/PUMA expression, reduced caspase activation, and mitigated cellular damage. Our findings establish Ca2+ overload-JUN activation as a central axis integrating oxidative, inflammatory, and apoptotic networks in obesity-aggravated LLIRI renal injury. Integrating multi-omics and pharmacological evidence, we identify JUN as a master transcriptional regulator of the Nox4-inflammasome-PUMA apoptotic triad, thereby elucidating a previously unrecognized pathogenic pathway in obesity-exacerbated renal LLIRI. Targeting this axis with calcium channel blockers is a promising therapeutic strategy.