Thomas Dempster (23 August 1579 – 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.