BACKGROUND: Gastric cancer is one of the most prevalent malignant tumors within the digestive system, and ferroptosis playing a crucial role in its progression. Glutathione peroxidase 4 (GPX4), a key negative regulator of ferroptosis, is highly expressed in gastric cancer and contributes to tumor growth. Targeting the regulation of GPX4 has emerged as a promising approach to induce ferroptosis and develop effective therapy for gastric cancer. METHODS: To confirm that OTUD5 is a deubiquitinase of GPX4 and regulates ferroptosis, we performed Western blotting, Co-IP, immunofluorescence, quantitative real-time PCR, Ub assay and flow cytometry experiments. To explore the physiological function of OUTD5, we knocked out the Otud5 gene in the mouse gastric cancer cell line (MFC) using CRISPR-Cas9 and eatablished the subcutaneous tumour model. Immunohistochemistry (IHC) analysis was used to inveatigate the pathological correlation in human gastric cancer. RESULTS: We report that ovarian tumor domain-containing 5 (OTUD5) interacts with, deubiquitylates and stabilizes GPX4. OTUD5 depletion destabilizes GPX4, promotes lipid peroxidation and sensitizes gastric cancer cells to ferroptosis. Moreover, the p53 activator nutlin-3a suppresses OTUD5 transcription, leading to GPX4 degradation and ferroptosis of gastric cancer cells. Notably, only wild-type p53 has the capacity to inhibit OTUD5 transcription, while p53 mutations or deficiencies correlate with increased OTUD5 expression, promoting gastric cancer progression. Additionally, OTUD5 silencing and nutlin-3a-induced GPX4 degradation enhances the sensitivity of gastric cancer cells to ferroptosis in vivo. Subsequently, the p53/OTUD5/GPX4 axis is confirmed in clinical gastric cancer samples. CONCLUSION: Collectively, these findings elucidate a mechanism whereby p53 inactivation upregulates OTUD5 transcription to deubiquitylate and stablize GPX4, resulting in ferroptosis inhibition and gastric cancer progression. This discovery highlights the potential therapeutic value of targeting OTUD5 to promote ferroptosis in p53-inactivated gastric cancer. KEY POINTS: OTUD5 mediates GPX4 deubiquitination to regulate its stability. Deletion of OTUD5 promotes ferroptosis and inhibits tumor growth. Wild type p53 inhibits OTUD5 transcription, thereby promoting GPX4 degradation and inhibiting the development of gastric cancer. OTUD5, GPX4 expression and p53 activity are highly correlated and correlates with clinical progression in STAD.