Vasak Siwni (Armenian: Վասակ Սիւնի; d. 452) was an Armenian prince, who was the lord of the principality of Syunik from 413 to 452, and also served as marzban (margrave) of Sasanian Armenia from 442 from 452.^[1][2] He renounced Christianity and joined the Sasanian forces against the leaders of the Armenian rebellion in 450/1, which culminated in the defeat of the rebel forces at the battle of Avarayr.^[3]

You can help expand this article with text translated from the corresponding article in French. (October 2013) Click [show] for important translation instructions. View a machine-translated version of the French 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. Consider adding a topic to this template: there are already 6,170 articles in the main category, and specifying|topic= will aid in categorization. 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 French Wikipedia article at [[:fr:Vasak de Siounie]]; see its history for attribution. You may also add the template {{Translated|fr|Vasak de Siounie}} to the talk page. For more guidance, see Wikipedia:Translation.

The contemporary Armenian historians Elishe and Lazar Parpetsi both give differing reports of the aftermath of the battle, albeit with the same outcome.^[4] According to Elishe, the Iranian general Mushkan Niusalavurt was greatly upset at the heavy casualties the Iranians had suffered in the battle, and thus gave Vasak Siwni free rein in Armenia.^[5] However, this resulted in even more bloodshed and turmoil, which led to the protest of many Armenian notables, and also by Mushkan himself. As a result, Vasak was imprisoned, while Adhur-Hormizd was installed the marzban of Armenia.^[6] According to Lazar, however, Mushkan was dismissed and sent back to Iran after he reported the Iranian losses to Yazdegerd II, who then appointed Adhur-Hormizd as the marzban of Armenia.^[7] Not long after, Vasak was imprisoned due to his deception towards the Armenians which had caused further turmoil.^[8]