Taraxacum coreanum Nakai has been traditionally used for treating inflammatory diseases including gastrointestinal diseases.We studied whether water extracts of Taraxacum coreanum Nakai (TCN) had a protective effect on acute and chronic gastritis induced by ethanol/HCl in an animal model of gastritis and its mechanism was also explored.In the acute study, rats were orally administered 0.15g/mL dextrin (normal-control), 0.15g/mL dextrin (control), 0.05g/mL TCN (TCN-L), 0.15g/mL TCN (TCN-H), or 0.01g/mL omeprazole (orally; positive-control), followed by oral administration of 1mL of 60% ethanol plus 150mM HCl (inducer). In the chronic study, rats were administered 10% diluted inducer in drinking water, and 0.6% dextrin, 0.2% or 0.6% TCN, and 0.05% omeprazole were administered in chow for 4 weeks. Acid content, gastric structure, oxidative stress, and markers of inflammation in the stomach tissue were measured at the end of experiment.Acute and chronic ethanol/HCl administration caused the inner layer of the stomach to redden, hemorrhage, and edema in the control group; TCN-H reduced these symptoms more effectively than did the omeprazole positive-control. Acid production and total acidity in the stomach increased in the control group, which was markedly suppressed by omeprazole. TCN also reduced the acid production and acidity, but not to the same degree as omeprazole. H-E and PAS staining revealed that in the inner layer of the stomach, cellular structure was disrupted, with an increased nuclear size and thickness, disarrangement, and decreased mucin in the control group. TCN prevented the cellular disruption in the inner layer, and TCN-H was more effective than the positive-control. This was associated with oxidative stress and inflammation. TCN dose-dependently reduced the infiltration of mast cells and TNF-α expression in the inner layer of the stomach, and decreased lipid peroxides by increasing superoxide dismutase and glutathione peroxidase expression.TCN-H acutely and chronically protected against gastritis and gastric ulcer by reducing oxidative stress and inflammation, not by completely suppressing gastric acid production.