What is a synonym for epic poem?

Here are some synonyms for epic poem, depending on the specific nuance you want to convey:

Formal:

* Epos

* Heroic poem

* National epic

* Chanson de geste (specifically for medieval French epics)

Less formal:

* Heroic ballad

* Long narrative poem

* Verse saga

Informal:

* Big story in verse

* Grand adventure poem

The best synonym will depend on the context and the specific features of the epic poem you're referring to.