The Girdle of Thomas, Virgin's Girdle, Holy Belt, or Sacra Cintola in modern Italian, is a Christian relic in the form of a "girdle" or knotted textile cord used as a belt, that according to a medieval legend was dropped by the Virgin Mary from the sky to Saint Thomas the Apostle at or around the time of the Assumption of Mary to Heaven. The supposed original girdle is a relic belonging to Prato Cathedral in Tuscany, Italy and its veneration has been regarded as especially helpful for pregnant women. The story was frequently depicted in the art of Florence and the whole of Tuscany, and the keeping and display of the relic at Prato generated commissions for several important artists of the early Italian Renaissance. The Prato relic has outlasted several rivals in Catholic hands, and is the Catholic equivalent of the various relics held by Eastern Christianity: the Cincture of the Theotokos of the Eastern Orthodox Church and the Holy Girdle of the Syriac Orthodox Church.

Thomas the Apostle, also known as Didymus, was one of the Twelve Apostles of Jesus according to the New Testament. Thomas is commonly known as "Doubting Thomas" because he initially doubted the resurrection of Jesus Christ when he was told of it ; he later confessed his faith on seeing the places where the wounds had healed on the holy body of Jesus after the Crucifixion of Jesus. While it is often assumed he touched the wounds in art and poetry, the scriptures do not say that he touched the wounds.