Background and Aims Hypoxia is a key feature of the tumor microenvironment of hepatocellular carcinoma (HCC) and contributes to tumor progression through hypoxia-inducible factor (HIF)-mediated regulation of multiple tumor-promoting genes. This study aimed to investigate the relationship between ring finger protein 24 (RNF24) and hypoxia/HIF-1α, evaluate RNF24 expression and its prognostic significance in HCC, and explore its effects on the malignant biological behaviors of HCC cells under hypoxic conditions and the underlying mechanisms.Methods The correlation between RNF24 and HIF-1α expression and the clinicopathological significance of RNF24 were analyzed using transcriptomic data from the TCGA-HCC cohort. RNF24 protein expression was examined by immunohistochemistry in tumor and paired adjacent tissues from 35 patients with HCC. Kaplan-Meier analysis and univariate and multivariate Cox regression analyses were performed to evaluate the prognostic significance of RNF24. Hypoxia was simulated by culturing cells under 1% O₂, HIF-1α knockdown and DMOG treatment were used to investigate the regulation of RNF24 by HIF-1α. RNF24 knockdown, CCK-8, and Transwell assays were performed to assess the effects of RNF24 on HCC cell proliferation, migration, and invasion under hypoxic conditions. Gene set enrichment analysis (GSEA), correlation analysis, qRT-PCR, and Western blot were further performed to investigate the potential molecular mechanisms underlying the biological effects of RNF24.Results TCGA analysis showed that RNF24 expression was positively correlated with HIF-1α expression. Hypoxia and DMOG treatment significantly increased RNF24 expression in HCC cells, whereas HIF-1α knockdown markedly attenuated hypoxia-induced RNF24 upregulation, suggesting that RNF24 is regulated by HIF-1α. RNF24 expression was significantly higher in HCC tissues than in corresponding adjacent tissues in both the TCGA cohort and the clinical cohort. High RNF24 expression was associated with aggressive clinicopathological features, including advanced TNM stage, higher T stage, and vascular invasion. Kaplan-Meier analysis showed that patients with high RNF24 expression had poorer overall survival rate and disease-free survival rate. Multivariate Cox regression analysis identified high RNF24 expression as an independent risk factor for poor prognosis in HCC (HR=1.407, 95% CI=1.058-1.872, P=0.019). Functional assays demonstrated that hypoxia promoted HCC cell proliferation, migration, and invasion, whereas RNF24 knockdown markedly attenuated these effects. GSEA showed that high RNF24 expression was associated with enrichment of the mTOR signaling pathway. Moreover, RNF24 knockdown reduced the expression of HIF-1α and its target genes, including VEGFA, TWIST, MMP2, and GLUT1.Conclusion RNF24 is a hypoxia-responsive gene regulated by HIF-1α and is highly expressed in HCC tissues. High RNF24 expression is associated with aggressive clinicopathological characteristics and poor prognosis. RNF24 contributes to hypoxia-induced HCC cell proliferation, migration, and invasion and may exert its tumor-promoting effects by enhancing HIF-1α and its downstream target gene expression. RNF24 may serve as a potential molecular biomarker and therapeutic target for HCC progression.