This study investigated the in vivo protective effect of cyanidin 3-glucoside (C3G) against ethanol-induced gastric lesions in rats. The experimental rats were treated with 80% ethanol after pretreatment with various doses of C3G (4 and 8 mg/kg of body weight), and the control rats received only 80% ethanol. Oral pretreatment with C3G significantly inhibited the formation of ethanol-induced gastric lesions and the elevation of the lipid peroxide level. In addition, pretreatment with C3G significantly increased the level of glutathione and the activities of radical scavenging enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, in gastric tissues. These results suggest that the gastroprotective effect of C3G removes the ethanol-induced lipid peroxides and free radicals and that it may offer a potential remedy for the treatment of gastric lesions.