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The present study evaluated the acute oral toxicity and in vivo anti-inflammatory activity of the methanolic leaf extract of Rumex hastatus (RHLM). In the acute toxicity study, mice received RHLM at 250, 500, 1000 and 2000 mg/kg and were observed for 14 days. No mortality or notable adverse behavioural changes were reported up to 2000 mg/kg, and body-weight gain remained comparable with the control group. Hematological indices and biochemical markers of hepatic and renal function showed no notable treatment-related alterations. Anti-inflammatory activity was evaluated in carrageenan- and formalin-induced rat hind-paw edema models. In the carrageenan model, RHLM at 200 and 400 mg/kg reduced paw edema over 5 h; at 5 h, percentage inhibition was 36.12±1.75% and 61.42±1.03%, respectively, compared with 61.58±1.34% for indomethacin (10 mg/kg). In the formalin model, RHLM reduced edema across the six-day observation period, with the 400 mg/kg dose showing the greatest effect. On day 6 at 3 h, inhibition was 57.55±3.45% with RHLM 400 mg/kg, compared with 55.21±3.05% for diclofenac (5 mg/kg). These findings indicate that RHLM was well tolerated in the reported acute toxicity study and demonstrated marked anti-inflammatory activity, particularly at 400 mg/kg.