Robert Blackadder (fl. 1483-1508) is important as diplomatist and first archbishop of Glasgow. He studied at St Andrews and Paris and, without becoming a monk, was abbot of Melrose (1471–76). He was bishop-elect of Aberdeen when translated to Glasgow. Support for the rebels against James III (1488) gave him an important role in the government of James IV. James and parliament supported the creation of an archbishopric by the Pope (1492): Blackadder's suffragans were Argyll, Galloway, Dunblane and Dunkeld. Reasons for the creation of a second archbishopric in Scotland were Blackadder's ambition, the alleged danger of having ecclesiastical power vested in only one archbishop, and the dignity of the nation.
Blackadder was frequently in Rome after 1471. He was involved in seeking a bride for James: at the French and Spanish courts (Ferdinand and Isabella asked for him to be made a cardinal), and in the marriage treaty with England (1502). Blackadder solemnised the marriage between James IV and Margaret, daughter of Henry VII of England (1503).
Blackadder was twice forced to confirm the cathedral chapter's privileges after disputes. He vaulted the "Blackadder Aisle" in the cathedral and founded two altars against the choir screen, the platforms for which survive. He founded chaplaincies at three of the cathedral's altars and, in honour of St Kentigern, a church at Culross. He annexed revenues from five parish churches to the university. He left money to both houses of friars in the city, to the poor, and to complete his work in the cathedral. In 1508 Blackadder visited Venice where he made his Will. He died a pilgrim en route to Jerusalem.