Cadmium (Cd) is a prevalent and toxic heavy metal widely present in soils. Cotton ( Gossypium hirsutum L.), which readily accumulates Cd, exhibits inhibited seed germination under Cd stress. Melatonin (MT), a potent indoleamine antioxidant, has been demonstrated to facilitate seed germination under adverse conditions, but its regulatory mechanisms in cotton under Cd stress remain unclear. In this study, cotton seeds of the cultivar ‘Nongda 601’ were used to investigate the effects of exogenous M