For the computer programming language, see Aldor.

In J.R.R. Tolkien's Middle-earth legendarium, Aldor was the third King of Rohan.

Aldor became King at the death of his father Brego in (T.A. 2570), aged only 26. He was the second son of Brego, his elder brother Baldor had been lost on the Paths of the Dead.

Aldor's rule was a golden age for Rohan, as the numbers of the Rohirrim increased, and the Dunlendings were chased past the Gap of Rohan beyond the borders of Adorn and Isen.

He also established Dunharrow as a refuge.

Aldor ruled for 75 years, and became known as Aldor the Old. He died in T.A. 2645 aged 102, a year after the birth of his first great-great-grandson. He was followed by his son Fréa.