Background: Ulcerative colitis (UC), a chronic inflammatory condition of the colon with no definitive cure, necessitates the exploration of innovative therapies. Herbal remedies combined with conventional drugs may offer complementary benefits, enhancing treatment outcomes. Objectives: This study investigates the therapeutic effects of Heracleum lasiopetalum Boiss in a rat model of acetic acid-induced UC. Methods: Forty-eight adult female Wistar rats were randomly allocated to six groups (n = 8 per group) for each of two experiments. UC was induced by intracolonic administration of 1 ml of 4% acetic acid for 10 minutes. In the treatment groups, female rats received an oral gavage of 5%, 10%, and 40% aqueous plant extract, sulfasalazine (100 mg/kg), and distilled water for 6 days, starting 3 days after acetic acid administration. The protective groups received substances via oral gavage from 7 days before to 3 days after acetic acid administration. The extent of mucosal ulcers, hyperemia, inflammation, and mucosal bleeding was evaluated based on the Gerald Classification System Score (Macroscopic). Pathological assessment was conducted on prepared slides using the modified Wallace method (Microscopic). Changes in body and colon weight, along with food and water intake, were examined. Results: Significant changes in food intake were observed in both the extract and positive control treatment groups, exhibiting a notable difference compared to the negative control group (P < 0.05). Body weight changes experienced a significant increase in the positive control treatment group compared to the negative control group (P < 0.05), while no significant difference was evident between the extract and negative control treatment groups (P > 0.05). In terms of water and food intake, as well as weight changes, no significant differences were detected among the various protective groups (P > 0.05). Both microscopic and macroscopic examinations revealed a substantial enhancement in the colon of the extract and positive control treatment groups compared to the negative control group (P < 0.05), with no significant difference observed between the protective groups (P > 0.05). Conclusions: Heracleum lasiopetalum extract demonstrates a dose-dependent reduction in colon hyperemia, mucosal ulceration, inflammation, and fibrosis. This highlights its potential as a supplementary treatment option for UC, emphasizing the need for further investigation.