The greatest of all rivers. It is the river Thor waded when he journeyed to the stronghold of Geirröðr. When he was mid-current, the water waxed so greatly that it came to his shoulders. Then Thor sang:
- Wax thou not now, Vimur,
- For I fain would wade thee
- Into the Giants' garth:
- Know thou, if thou waxest,
- Then waxeth God-strength in me
- As high up as the heaven.
The rising was caused by the giantess Gjálp. Thor stops her by throwing a huge rock at her. He wades to the shore and takes hold of a rowan-clump, and so climbs out of the river; from this comes the saying that rowan is Thor's deliverance.
In a verse in Húsdrápa by Úlfr Uggason, and quoted by Snorri Sturluson in Skáldskaparmál, Thor is called Vimur's ford's Wide-Grappler.
- Skáldskaparmál, 4, 18.