Hereward the Wake (c. 1035 – 1072), known in his own times as Hereward the Outlaw or Hereward the Exile, was an 11th-century leader of local resistance to the Norman conquest of England.

Hereward's base was in the Isle of Ely, and according to legend he roamed The Fens, covering North Cambridgeshire, Southern Lincolnshire and West Norfolk, leading popular opposition to William the Conqueror. The name Hereward is composed of Old English roots here = army, and weard = guard, and is cognate with Old High German Heriwart and modern German Heerwart. The title "the Wake" (meaning "watcher") was popularly assigned to him many years after his death.

Several primary sources exist for Hereward's life, though the accuracy of their information is difficult to evaluate. They are the version of the Anglo-Saxon Chronicle written at Peterborough Abbey (ASC), the Domesday Book (DB), the Liber Eliensis (Book of Ely) and, much the most detailed, the Gesta Herewardi (Gesta). To a small extent, they are sometimes mutually contradictory. This probably indicates, as the preface to the Gesta suggests, that conflicting oral legends about Hereward were already current in the Fenland in the late eleventh and early twelfth centuries. In addition, there may be some partisan bias in the early writers: the notice of Hereward in the Peterborough Chronicle, for instance, was written in a monastery which he was said to have sacked, some fifty years after the date of the raid. On the other hand, the original version of the Gesta was written in explicit praise of Hereward,; much of its information was provided by men who knew him personally, principally, if the preface is to be believed, a former colleague in arms and member of his father's former household named Leofric the Deacon.