Thomas Fairfax, third Baron Fairfax of Cameron, in the Scottish peerage, grand-nephew of the preceding, a parliamentary general in the civil wars of Charles I., born at Denton, Yorkshire, in January, 1611, died at Bilburgh, near York, Nov. 12, 1671. He studied at St. John's college, Cambridge, served as a volunteer in Holland, under the command of Lord Vere, whose daughter he afterward married, returned to England in 1634 or 1635, and lived in retirement till the breaking out of the war in 1642. When the king set about raising a guard for his person at York, Fairfax presented himself at the head of a multitude of 100,000, praying that he would return and hearken to his parliament. The first hostilities occurring in Yorkshire, Fairfax's father, Ferdinando, second Lord Fairfax, was made general of the parliamentary forces in the north, with himself (then Sir Thomas Fairfax) as his general of the horse. They were denounced as traitors by the earl of Newcastle, the royal commander in those parts, who in turn was proclaimed a traitor by the parliament.

The Fairfaxes were defeated in several encounters, and completely routed in an attack upon the royalist forces under the earl of Newcastle at Atherton Moor. The first parliamentary success of 1644 was that of Nantwich, in Cheshire, where Sir Thomas Fairfax defeated Byron with great loss, and Monk, the future restorer of the monarchy, was taken prisoner. Fairfax then joined the Scotch army, which to the number of 20,000, under the command of Lord Leven, had crossed the Tyne, and united with the earl of Manchester's army, in which Cromwell was major general. At Marston Moor, near York, on July 2, Fairfax gained a temporary success; but the victory was decided only by the steady valor of the republicans under Cromwell. York was immediately forced to surrender, and Sir Thomas quickly reduced the remaining royalist fortresses north of the Trent, and after the passage of the self-denying ordinance in 1645 received from parliament the appointment of commander-in-chief. On April 3 he departed for Windsor, where with the assistance of Cromwell, who was his lieutenant, he set about remodelling the army. On June 14 the hostile forces met at Naseby, where Fairfax and Cromwell pierced the royalist ranks in all directions. The personal valor of Fairfax was especially signalized in this battle.

He was constantly in the thickest of the fight, and rode about bareheaded after his helmet was beaten to pieces. He now quickly recovered Leicester, Langport, Bridgewater, and Bath. Bristol soon surrendered, and the speedy reduction of the kingdom followed, Fairfax and Cromwell having to this end divided their forces. In the politics of the dominant party Fairfax had now to play the difficult part of a sincere advocate of monarchical power. He seems to have been led on by Cromwell, and to have been the instrument of projects whose depth he could not fathom. In 1648 he annihilated the last remains of the royalist party at Colchester. His own influence declined as that of Cromwell and the Independents increased; and though his loyal instincts recoiled from the judicial trial of the king, he was unable to prevent it. He accepted the command of all the- forces of England and Ireland under the new government, put down the Levellers in Oxfordshire,' and composed the troubles in Hampshire. When in 1650 the Scots declared for Charles II., he refused to march against them, and laid down his commission.

When Monk entered England, Fairfax took possession of York, Jan. 1, 1660. He gave his consent to the restoration of the monarchy, and presented to King Charles the horse on which he rode to his coronation, after which he went into retirement. Lord Fairfax was a friend of learning, and in his youth devoted much attention to antiquarian studies. During the siege of York, when a tower containing many ancient documents was blown up, he rewarded the soldiers for bringing him as many as could be found, and employed Roger Dods-worth to copy them; they now make a part of the Monasticon Anglicanum. When he took possession of Oxford, June 24, 1646, he set a guard over the Bodleian library, which otherwise might have been destroyed. He wrote a narrative of his career from the commencement of the war, not intended for the public eye, but which was published in 1699 under the title of Short Memorials of Thomas, Lord Fairfax."-See The Fairfax Correspondence," edited from the family manuscripts by Robert Bell (4 vols., London, 1849); and "Life of the Great Lord Fairfax," by C. R. Mark-ham (1870).