Smbat VI Bagratuni (ca. 670 – 726) was a member of the Bagratuni family who was presiding prince of Armenia with interruptions from 691 to the 710s. During his reign, he frequently shifted alliances between the Byzantines, who gave him the title of, and the Umayyads. He was the son of Varaz-Tirots III Bagratuni, and the uncle of Ashot III Bagratuni.
In the early 690s, Armenia was in turmoil, as the country was being disputed between the Byzantine Empire and the Umayyad Caliphate: taking advantage of the civil war of the Second Fitna in the Caliphate, the Byzantine emperor Justinian II had invaded Armenia and installed his own candidate, Nerses Kamsarakan, as its presiding prince, while Kamsarakan' predecessor, Ashot II Bagratuni, was killed in 690 fighting against a retaliatory Arab invasion. The Armenian sources accuse the Byzantine troops of pillaging the country, taking hostages for ransom, and trying to impose a communion between the Miaphysite Armenian Church and the Chalcedonian Byzantine Church. As a result, the Armenians soon came to see the Arabs as liberators.
Nerses Kamsarakan's tenure was brief, and he was succeeded by Smbat Bagratuni, who had served as commander-in-chief under Kamsarakan. Smbat had particular reason to hate the Byzantines: his father, Varaz-Tirots, had been assassinated by them.
When the Umayyads, after the end of the civil war, returned in force to Armenia in 693 under Muhammad ibn Marwan, Smbat defected to their side, and even had the captured Byzantine soldiers mutilated and executed, in vengeance for his father. According to the 8th-century Armenian historian Łewond, who places the incident in 698, Smbat confronted a Byzantine army sent to Armenia by Emperor Tiberius III "at the swamps of Paik". The battle was bloody and indecisive; Smbat and his men retreated from the battlefield, but the exhausted Byzantines abandoned their invasion in turn.
Thanks to his betrayal of the Byzantines, Smbat was confirmed as "prince of the Armenians" by the Umayyads, but from 695 on, the Arabs' previous policy of tolerance and respect for Armenian autonomy was abandoned. Muhammad's troops plundered the country, and systematically persecuted the Armenian nobles and confiscated their possessions. When Muhammad left, he left an Arab governor in the country, Abdallah ibn Hatim al-Bahili, who continued this policy; even the Armenian patriarch, Sahak III, and Smbat himself, were for a time sent as prisoners to the Umayyad capital, Damascus.
After being released, sometime before 700, Smbat decided to defect to the Byzantines. He gathered his followers north of Mount Ararat, including the prince of Vaspurakan, also named Smbat, and Vard Rhstuni, whose father Theodore had played a central role in the submission of Armenia to the Arabs in the 650s. Smbat's forces, numbering some 2,000, began their march to Byzantine territory in the winter. The 8,000-strong Umayyad garrison at Nakhchivan pursued them, but the Arabs, unaccustomed to the harsh winter conditions, were defeated with heavy loss near Vardanakert; reportedly, only 300 of them survived the battle and the cold to reach safety. Smbat pursued them up to the walls of the fortress of Erenjak, whose ruler, the lady Shushan, moved by pity, offered the Arabs sanctuary and persuaded Smbat to call off his pursuit.
Smbat sent ahead to Constantinople with news of his victory. He was welcomed by the Byzantines, given the high title of, and settled at Tukhark in the border region of Tayk. There Smbat awaited an opportunity to return to his homeland. This arose in 705, when many Armenian nobles were convened by the Umayyad authorities on the pretext of being registered for military service, but were instead burned alive in churches at Nakhchivan and Khramm. At the head of a Byzantine force, Smbat invaded Armenia, but was defeated and had to retreat, establishing himself this time at the Poti on the Black Sea coast, likely an indication that the Arabs menaced his former base.
In 711, at least in part in reaction to renewed ecclesiastic pressure on the Armenian Church in the lands controlled by the Byzantines, Smbat again switched sides: he plundered the local churches and the villa granted to him by the emperor, seized the treasury of the town, and defected to the Arabs. The Byzantines excommunicated him, but the Arabs, who had now switched again to a more accommodating policy, welcomed him with open arms and restored him as presiding prince of Armenia. According to the historian Joseph-François Laurent, Smbat was the "most typical example" of the tendency of the Armenian princes to switch sides between Byzantium and the Caliphate, whenever they quarreled with either one of the two great powers of the region.
Nothing further is recorded of his fate; the next known presiding prince was his relative, Ashot III Bagratuni.