Thomas, Sixth Lord Fairfax (October 22, 1693-December 9, 1781) was born at Leeds Castle, in Kent, England, the son of Thomas, Fifth Lord Fairfax, and Lady Catherine Culpeper Fairfax. It was through his mother that he inherited five million acres in Virginia. The land included much of the present Eastern Panhandle of West Virginia.

Fairfax was a student at Oxford University when his mother died in 1719. He took control of his land holdings in 1732 at the death of his agent, Robert "King" Carter. Fairfax first visited his land in Virginia in 1735, and in 1748 hired a surveying party that included the teenage George Washington to mark its boundaries. A boundary dispute with the Virginia government caused Lord Fairfax to return to England in 1737 to argue his case. The dispute was settled in his favor in London in 1745.

In 1747, Lord Fairfax took up permanent residence in the Virginia colony to supervise his land holdings. In 1752, he built Greenway Court, at the village of White Post, near Winchester, and became active in civil, local military, and religious affairs. Fairfax steered a careful path politically, and neither he nor his property was molested during the Revolutionary War by either Americans or British. He died at Greenway Court and is buried at Christ Church in Winchester.

Lord Thomas Fairfax never married. His brother, Robert Fairfax, became the Seventh Lord Fairfax, and the line continues today in London with Nicholas, 14th Lord Fairfax, Baron of Cameron.