You can help expand this article with text translated from the corresponding article in Vietnamese. (November 2015) Click [show] for important translation instructions. View a machine-translated version of the Vietnamese article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Vietnamese Wikipedia article at [[:vi:Hoành Sơn (dãy núi)]]; see its history for attribution. You may also add the template {{Translated|vi|Hoành Sơn (dãy núi)}} to the talk page. For more guidance, see Wikipedia:Translation.

Hoành Sơn Range is a mountain range in the North Central Coast region of Vietnam. The range runs from Annamite Range to the South China Sea in southern Hà Tĩnh Province and northern Quảng Bình Province. It's the natural borderline of these two provinces.^[1] The length of this range is about 50 km. It crosses National Route 1 in Ngang Pass.

The Hoành Sơn mountains once served as a natural barrier between Dai Viet and Champa from 938 to 1069 when it was annexed by Vietnamese Lý dynasty and the site of the 30 km-long Kỳ Anh barrier built by Champa.^[2] The border of two countries was moved to the north of Quảng Trị province