Like the adjacent Pilgrimage Window (n25), the Martyrdom Window is of the ‘band’ type, with two bands of full-colour panels set between three bands of pale grisaille glass. Its name reflects the seven martyrdoms depicted in it. The lower colour band is given over to donors and a Virgin and Child, and the upper one to three martyrdoms (of St Lawrence, St Denis and St Vincent); the lowest grisaille band has the martyrdom of St Edmund, and the central one that of St Stephen. The tracery contains depictions of two further martyrs, St Peter and St Paul (who witnessed the martyrdom of St Stephen), crowned by Christ enthroned in Majesty.
It is not known for certain who the donor was, or indeed if there was more than one. A clue as to one figure associated with the window may lie in the heraldic borders of the outer lights, which have the arms of the Mowbray family, Gules a lion rampant argent, and the Clare family, Or three chevrons gules. These arms point to John de Mowbray, 2nd Baron: his father was Roger de Mowbray (1254–1297) and his mother was Rose de Clare (b. c.1252, daughter of Richard de Clare, 6th earl of Gloucester). John de Mowbray was appointed governor of York in 1312 and in 1322 fought with a group of rebellious barons against Edward II at the Battle of Boroughbridge; he was hanged afterwards for treason. It is interesting that a later governor of York, Sir Simon de la Warde, who fought on the king’s side at the Battle of Boroughbridge, may have donated the adjoining Pilgrimage Window. In the lower left of the window there is a lay male donor figure identified as Vincent; in the lower right corner are two further lay donor figures, one male and one female, neither identified. No connection has yet been established between John de Mowbray and a Vincent.