The battle of Thetford occurred in 1004. Sigvat records the victory of King Ethelred, allied with Olaf Haraldsson,^[1] over the Danes under Sweyn Forkbeard during the latter's campaigns in England.

The battle site was located in lands under the control of Ulfcytel Snillingr, then of East Anglia, at a site once thought to be near Wretham,^[1] but now thought to be at Rymer in Suffolk.^[2] The Anglo-Saxon Chronicle reports that the battle of Thetford occurred after an attempt by Ulfcytel and the "councillors in East Anglia" to negotiate a truce with Sweyn in return for a financial settlement; the Danes broke the truce, and marched on Thetford where they were met and engaged by a contingent of the East Anglian fyrd.