Tostig Godwinson (died 25 September 1066) is an Anglo-Saxon Earl of Northumbria and brother of King Harold Godwinson.

Tostig is the third son of Godwin (d. 1053), Earl of Wessex and Kent, and Gytha, daughter of Thorgils Sprakaleg.

In 1051, he marries Judith, the daughter of Count Baldwin IV of Flanders, half-sister of Baldwin V of Flanders, and aunt of Matilda of Flanders, who marries William the Conqueror.

The Domesday Book records twenty-six vills or townships as being held by Earl Tostig, forming the Manor of Hougun.