Thomas Dempster (23 August 1579[1] – 6 September 1625) was a Scottish scholar and historian. Born into the aristocracy in Aberdeenshire, which comprises regions of both the Scottish highlands and the Scottish lowlands, he was sent abroad as a youth for his education. The Dempsters were Catholic in an increasingly Protestant country and had a reputation for being quarrelsome. Thomas' brother James, outlawed for an attack on his father, spent some years as a pirate in the northern islands, escaped by volunteering for military service in the Low Countries and was drawn and quartered there for insubordination. Thomas' father lost the family fortune in clan feuding and was beheaded for forgery.
For these and political and religious reasons in these often violent Elizabethan times Thomas was unable to come home except for visits. Of uncommon and impressive height and intellectual ability he became an itinerant professor in France and Italy, driven from place to place by a series of colourful personal incidents in which he fought duels or opposed officers of the law. He eventually found refuge and patronage under Grand Duke Cosimo II of Tuscany, who commissioned a work on the Etruscans. Three years later Thomas handed the duke a magnum opus, the manuscript of De Etruria Regali Libri Septem, "Seven Books about Royal Etruria",[2] in the Latin language, the first detailed study of every aspect of Etruscan civilisation, considered a brilliant work. In 1723 Thomas Coke finally undertook to publish an enhanced edition of it. The original manuscript remains in Coke's library at Holkham.