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The production of saffron, the spice obtained from the dried stigmas of Crocus sativus L. (Iridaceae family) flowers, generates, after pruning, considerable quantities of waste containing natural dyes. Saffron flower waste could be a source of extraction of natural dyes with antioxidant activity. In this study, we investigate the possibility of using saffron flower waste for dyeing cotton and evaluating the antioxidant effect of this dye by the DPPH free radical, reducing power and ß-carotene bleaching assay. The dye has been evaluated for the composition of the color by the UV-visible spectrum and tested for the dyeing of cotton. The results indicate the presence of polyphenols and flavonoids. The dyeing conditions have been optimized at 6% dye concentration, dye bath pH of 3, dyeing temperature at 98 °C and dyeing time of 60 min. 2% dye concentration with 5 to 10% mordant concentration remains sufficient for dyeing with pre-mordanting. The exhaustion of the bath after dyeing has been improved by a rate of 20% in the case of addition of mordants which have produced a shade of green color. The dye contributes to the significant antioxidant activities with more DPPH scavenging capacity, FRAP reducing power, and ß-carotene bleaching inhibition. Cotton fabrics dyed with bio-dyes obtained from saffron flower waste show good color fastness properties and could be a potential source of natural antioxidant agent. It presents an important eco-friendly alternative to synthetic dyes for large-scale application in textile and food industries. [ABSTRACT FROM AUTHOR]