Robert Blackadder was a medieval Scottish cleric, diplomat and politician, who was abbot of Melrose, bishop-elect of Aberdeen and bishop of Glasgow; when the last was elevated to archiepiscopal status in 1492, he became the first ever archbishop of Glasgow. Archbishop Robert Blackadder died on 28 July 1508, while en route to Jerusalem on pilgrimage.
Robert was the younger brother of Patrick Blackadder of Tulliallan, a middling Fife laird. Robert studied at the University of St Andrews (where his name is listed among the students in either 1461 or 1462), and in 1464 he was received as a bachelor in the University of Paris. The following year, 1465, he graduated as licentiate. In 1471 King James III of Scotland sent him as a messenger to Pope Paul II. It was probably while at Rome that Robert secured from the pope the abbacy of Melrose. This was the first time a non-Cistercian had become abbot at Melrose, and moreover the pope granted Blackadder leave to take the abbacy without becoming a monk. This did not go down well with the monks at Melrose. One monk, Richard Lamb, challenged this decision at the papal court. Lamb had the support of the bishop of Glasgow, John Laing, and of the monks at Melrose. Several years of litigation followed, and after being offered a substantial pension, Blackadder resigned the abbacy in 1476. In 1477 Blackadder's name is recorded in a letter of Pope Sixtus IV, where it is said that the pope had received a petition from "Robert Blakidir", a rector of the church of Lasswade in the diocese of St Andrews, requesting permission to build a hospital near the church. Permission and funds were granted, and so came into being the Hospital of St Mary of Consolation. A year later, the pope granted Blackadder permission to convert the church of Lasswade into a prebend of the church of St Salvador in St Andrews, specifying that the holder must have a licentiate or doctorate.