Background: Curcuma longa (turmeric) has been widely utilized in Ayurveda, Traditional Chinese Medicine, and Unani for the treatment of inflammatory and metabolic problems. The principal bioactive ingredient, curcumin, demonstrates anti-inflammatory, antioxidant, and immunomodulatory characteristics. Objective: This systematic review sought to rigorously investigate randomized controlled trials (RCTs) regarding the efficacy and safety of Curcuma longa extracts in inflammatory and metabolic illnesses. Methods: In accordance with PRISMA rules, databases such as PubMed, Embase, Cochrane CENTRAL, Web of Science, and prominent Chinese repositories were examined till February 2025. Randomized controlled trials (RCTs) examining Curcuma longa or curcumin (administered orally or topically) for arthritis, inflammatory bowel disease, type 2 diabetes, dyslipidemia, metabolic syndrome, or associated conditions were included. The evaluated outcomes included clinical indicators (e.g., pain scores, glycemic control), biochemical markers (e.g., CRP, IL-6, lipid profile), and safety metrics. The Cochrane methodology was utilized to assess the risk of bias, and meta-analyses were performed when possible. Results: Twenty randomized controlled trials including 1,754 participants were considered. Curcuma longa markedly alleviated pain (mean difference [MD] −1.2; 95% CI −1.6 to −0.8) and enhanced WOMAC and DAS28 scores in arthritis. It also reduced levels of CRP, ESR, IL-6, and TNF-α. In metabolic diseases, curcumin enhanced HbA1c (MD −0.6%; 95% CI −0.8 to −0.4), fasting glucose, LDL, triglycerides, and elevated HDL levels. Markers of oxidativestress diminished, accompanied by enhanced activity of antioxidant enzymes. Adverse effects were minor, primarilygastrointestinal, and dosages of up to 12 g/day were well tolerated. Conclusion: Extracts of Curcuma longa exhibitconsiderable promise as a supplementary treatment for inflammatory and metabolic illnesses, providing clinicallysignificant enhancements in pain, inflammation, and metabolic indicators with a favourable safety profile.Comprehensive, long-term randomized controlled trials with standardized, bioavailability-enhanced formulations arenecessary to validate these results and improve clinical integration.