1911 Encyclopædia Britannica/Tostig
TOSTIG (d. 1066), earl of Northumbria, was a son, probably the third, of Earl Godwine, and in 1051 married Judith, sister or daughter of Baldwin V., count of Flanders. In the year of his marriage he shared the short exile of his father, returning with him to England in 1052, and became earl of Northumbria after the death of Earl Siward in 1055. He was very intimate with his brother-in-law, Edward the Confessor, and in 1061 he visited Pope Nicholas II. at Rome in the company of Aldred, archbishop of York. By stern and cruel measures Tostig introduced a certain amount of order into the wild northern district under his rule; this severity made him exceedingly unpopular, and in 1065 Northumbria broke into open revolt. Declaring Tostig an outlaw and choosing Morkere in his stead, the rebels marched southwards and were met at Oxford by Earl Harold, who, rather against the will of the king, granted their demands. Tostig sailed to Flanders and thence to Normandy, where he offered his services to Duke William, who was related to his wife and who was preparing for his invasion of England. He then harried the Isle of Wight and the Kentish and Lincolnshire coasts, and, after a stay in Scotland and possibly a visit to Norway, joined another invader, Harald III. Hardrada, king of Norway, in the Tyne. Together they sailed up the Humber and at Gate Fulford, near York, defeated Earls Morkere and Edwine and entered York. But Harold, now king, was hurrying to the north. Taking the Norwegians by surprise at Stamford Bridge he destroyed their army on the 25th of September 1066, and in this battle both Tostig and the king of Norway were slain. Tostig’s two sons appear to have taken refuge in Norway, and his widow Judith married Welf, duke of Bavaria.
See E. A. Freeman, The Norman Conquest, vols. ii. and iii. (1870–1876).