Oiomúrë was a shoreland region of "great mists" in northern Aman, near the Helcaraxë.
Origin
Robert Foster has suggested that the mists of Oiomúrë may have been caused by "contact between the Grinding Ice and warmer sea water.".
After the Darkening of Valinor, Morgoth and Ungoliant fled the pursuing Valar northwards through the barren and cold land of Araman, traversing Oiomúrë and the Helcaraxë in order to reach Middle-earth.
The Noldor led by Fingolfin during their Flight possibly as well passed through Oiomúrë on their march to Beleriand from Valinor through the Helcaraxë.