This research evaluates the phytotoxic potential of methanolic extracts derived from Wedelia trilobata (L.) Hitchc. against major rice weeds and rice cultivars under controlled laboratory conditions. Six plant species were tested: three dominant weed species (Leptochloa chinensis, Echinochloa crus-galli, Fimbristylis miliacea), two rice varieties (Oryza sativa L.) OM380, OM5451), and green mustard (Brassica juncea) as an indicator species. The results indicated that root growth of F. miliacea and L. chinensis was completely inhibited (100%) at concentrations between 0.12 - 0.24 g/mL, while shoot elongation was reduced by over 85%. E. crus-galli exhibited only mild inhibition or slight stimulation at lower concentrations. Both rice cultivars showed dose-dependent sensitivity, with OM380 being more responsive to lower concentrations (0.03 g/mL). Phytochemical screening confirmed the presence of high levels of phenolic and flavonoid compounds, particularly in whole plant and leaf extracts (TPC: 158.11 mg GAE/g; TFC: 260.57 mg QE/g). These allelochemicals may interfere with germination and root development of target weeds, suggesting their potential as bioherbicidal agents. The findings highlight the allelopathic potential of W. trilobata for selective weed suppression in rice agroecosystems. Further studies should focus on isolating key bioactive compounds and assessing their efficacy under greenhouse and field conditions to support the...