The Vale of Arryn, often referred to simply as the Vale, is one of the constituent regions of the Westeros. Prior to the Targaryen Conquest, it was a sovereign nation known as the Kingdom of Mountain and Vale. It is ruled by House Arryn from their stronghold, the Eyrie. Protected and surrounded by the Mountains of the Moon, the Vale is isolated from the rest of Westeros and is accessible only during warmer seasons. Bastards born in the Vale are given the surname Stone.

The Vale is where the Andals first landed and assailed from during their invasion of Westeros six thousand years ago, though as settlement patterns became established, the Reach became the main population center and cultural heartland of the Andals. Still, because of its isolated, mountainous terrain, noble families from the Vale are said to have among the purest Andal bloodlines within Westeros. While some other noble families on the continent can claim the same, the Vale is unique to this as a region. There are many small tribes who inhabit the foothills of the Mountains of the Moon. These tribes are commonly known as the hill tribes, and they reject the rule of House Arryn. Although they are dangerous to passing travelers, their lack of organization and less advanced weaponry means they pose little threat to the rest of Westeros. 

During the War of the Five Kings, under the regency of Lady Lysa Arryn after the death of Jon Arryn, the Vale followed a strict policy of neutrality until the very last stages of the conflict and was thus able to keep its resources and army, the formidable knights of the Vale, nearly intact. The young Lord Robin Arryn, under the wing of the manipulative Lord Protector Petyr Baelish, consented to join the war when they came to the aid of their old allies of House Stark in their campaign to retake  Winterfell and the North from House Bolton at the Battle of the Bastards. In the aftermath of the battle, the lords of the Vale and the North hailed Jon Snow,  bastard of House Stark, as the King in the North, thus seceding from the sovereignty of the Iron Throne and joining the Kingdom of the North until Jon pledged himself to Daenerys Targaryen during her invasion. Robin Arryn then chose to recognize Bran Stark as the new King after Daenerys' assassination.

Unlike the the Westerlands, the mountains of the Vale are much less hospitable and more difficult to traverse. While the mountains of the Westerlands are filled with precious metals such as gold and silver, the mountains of the Vale are not particularly rich in resources. The valleys scattered between the harsh mountains, however, are as fertile as any in the Riverlands. The Vale's mountains are well-known for their strategic defensibility.

Notable places shown in the series are: