In the fictional world of Middle-earth created by J. R. R. Tolkien, Rhûn was a large region of eastern Middle-earth. Rhûn (which is also the Elvish word for "east") was the name used for all lands lying east of Rhovanion, around and beyond the inland Sea of Rhûn, from where came many attacks on Gondor and its allies during the Third Age of Middle-earth.
Rhun or Rhun Hir ap Maelgwn (died c. 586) was King of Gwynedd in Wales.
Rhun may also refer to:
- Rhun ab Owain Gwynedd (died 1146), son of Owain Gwynedd
- Rhûn, a fictional land in the writings of J. R. R. Tolkien
- Prince Rhun, character in the writings of Lloyd Alexander
Rhun is a Welsh Masculine given name meaning "Great, Mighty". Variants of the name are; Rhûn, Rhyn and Rhŷn.
One origin of the name appears to start from the the Welsh names for Rome and Roman (as a person), Rhufain and Rhufon, leading to Rhun as "the proper name of a man" and Rhyon as a soldier.