Ecgþeow (Proto-Norse *Agyþewaz [1].) was a warrior in Beowulf in the service of the Geats. In the epic we only learn that he belonged to a probably Swedish family (an ätt, see Norse clans) called the Waegmundings and that he had slain Heaðolaf, a man from another family called the Wulfings (probably the rulers of the East Geats). One of the Germanic ways of solving such an event was either to pay the wergild or to be banished. Apparently, Ecgþeow could not pay the wergild because he had to leave and go to Hroðgar, the Danish king. Hroðgar payed the wergild and had Ecgþeow swear an oath to him. Ecgþeow later married the daughter of the Geatish king, Hreðel, and had the son Beowulf.

When Beowulf arrived at Heorot, Hrothgar interprets this as a son's gratitude for what Hroðgar had done to Beowulf's father, and allows Beowulf to fight against Grendel.

Wiglaf and his father Weohstan were relatives of Ecgþeow.