Beleg of Arthedain was the second King of Arthedain. During his reign, or possibly the reign of his son, there were two things that occurred which, at the time, seemed inconsequential, but would prove to be quite significant many years later.

The first of these events was the appearance of a short, hairy-footed, Man-like people who came across the Misty Mountains. The Dúnedain called them 'Periannath' or 'Halflings' and they were the first Hobbits to enter into the realms of Men in the west of Middle-earth.

The second event was the coming of a shadow to the forest of Greenwood the Great. At first the shadow was of unknown origin, but either before Beleg's reign was ended, or shortly thereafter, the Wise discovered that its source was at Dol Guldur. The forest became a place of fear and was renamed Mirkwood during this time. Many years later it was realized that the shadow was a product of the return of Sauron himself. He hid there until he was able to return to Mordor. His final defeat is well documented in the end of the War of the Ring.

Beleg ruled Arthedain from TA 946 until TA 1027, and died in TA 1029. He was succeeded by his son Mallor.