I *belive* those particular cycles are Irish. More generally an Epic Cycle is a mythic narrative formed of the various quasi-historical tales.

Beowulf is all that remains of a much larger Anglo-Norse cycle while the Iliad and Odyssey are all that remain of the Greek Epic Cycle. In the case of the latter it stretches from the Beggining to after the Trojan War but moist of it is lost to us, though we do know much of the narrative.