Obesity is a major global health concern associated with metabolic syndrome, oxidative stress, and hepatic steatosis. The present study evaluated the anti-obesity potential of Calendula officinalis (marigold) leaf extracts prepared using different solvents (aqueous, hydroalcoholic, and ethyl acetate) in rats with diet-induced obesity. The extracts were characterized phytochemically for total phenolics, flavonoids, and HPLC profiles. Male Wistar rats were divided into groups: normal diet control, high-fat diet (HFD) control, HFD with low- and high-dose extracts, and a reference drug group (Orlistat). Treatments continued for 8–12 weeks, followed by assessments of body weight, lipid profile, oxidative stress markers, and liver histopathology. Among the extracts, the hydroalcoholic extract showed the most significant reduction in body weight gain, total cholesterol, triglycerides, and LDL levels, while increasing HDL concentrations. It also markedly improved antioxidant status (decreased MDA, increased SOD, GPx, and catalase activity) and ameliorated hepatic histopathological changes. The anti-obesity effect correlated with the extract’s phenolic and flavonoid content. Overall, C. officinalis leaf extracts—particularly the hydroalcoholic fraction—exhibited strong anti-obesity and antioxidant activity, likely through modulation of lipid metabolism and oxidative stress. These findings support further mechanistic and clinical evaluation of C. officinalis as a potential complementary therapy for obesity.