Ferroptosis is a new form of cell death, and inhibition of ferroptosis is a promising strategy to treat neurological diseases. In this work, sixteen compounds were isolated from Ajuga nipponensis and assayed for anti-ferroptosis activity in HT22 mouse hippocampal neuronal cells. Ajudecunoid C (1, ADC), a new neoclerodane diterpenoid, showed significant inhibitory activity against erastin and RSL3-induced ferroptosis with EC₅₀ values of 4.1?±?1.0 and 3.6?±?0.3?μM, respectively. Experimental results demonstrated that ADC effectively prevented ferroptosis through scavenging free radical and activating NRF2-antioxidant response elements (AREs) pathway. This study reveals that ADC, as a new ferroptosis inhibitor, is a promising lead compound for the development of drugs against ferroptosis-related neurological diseases.