William Turnbull (born approx. 1400) was an influential Bishop of Glasgow Scotland from 1448 to 1454.
He studied arts at the University of St Andrews (1419), canon law at Catholic University of Leuven, Belgium and studied at University of Pavia, Italy for a doctorate in canon law (1439).
Upon his return to Scotland, he befriended King James II and became Keeper of the Privy Seal (1440-1448) and Royal Secretary (1441-1442). In 1447 he was appointed Bishop of Dunkeld, then a year later Bishop of Glasgow.
During his time as Bishop, he pursued the formation of a University in Glasgow with the encouragement of King James II. On 7 January 1451, Pope Nicholas V issued a papal bull decreeing the foundation of the University of Glasgow, which started classes in the Glasgow Cathedral buildings.
