Yuwen Tai (Chinese: 宇文泰; pinyin: Yǔwén Tài) (505/7 – 21 November 556), nickname Heita (黑獺), formally Duke Wen of Anding (安定文公), later further posthumously honored by Northern Zhou initially as Prince Wen (文王) then as Emperor Wen (文皇帝) with the temple name Taizu (太祖), was the de facto ruler and paramount general of the Xianbei-led Chinese Western Wei dynasty, a branch successor state of the Northern Wei. In 534, Emperor Xiaowu of Northern Wei, seeking to assert power independent of the paramount general Gao Huan, fled to Yuwen's domain; when Gao subsequently proclaimed Emperor Xiaojing of Eastern Wei emperor, a split of Northern Wei was effected, and when Yuwen subsequently poisoned Emperor Xiaowu to death around the new year 535 and declared his cousin Yuan Baoju emperor (as Emperor Wen), the split was formalized, with the part under Gao's and Emperor Xiaojing's control known as Eastern Wei and the part under Yuwen's and Emperor Wen's control known as Western Wei. For the rest of his life, Yuwen endeavored to make Western Wei, then much weaker than its eastern counterpart, a strong state, and after his death, his son Yuwen Jue seized the throne from Emperor Gong of Western Wei, establishing the Northern Zhou dynasty.

Yuwen Tai was born in 505, and was a descendant of the last chieftain of the Xianbei Yuwen tribe Yuwen Yidougui, whose tribe was destroyed by Murong Huang, the founding ruler of Former Yan. Yuwen Yidougui's descendants served as generals during Former Yan and its successor state Later Yan. Later, when Emperor Daowu of Northern Wei defeated the Later Yan emperor Murong Bao (Emperor Huimin), Yuwen Tai's great-great-grandfather Yuwen Ling (宇文陵) surrendered to Northern Wei, and was relocated to Wuchuan (武川, in modern Hohhot, Inner Mongolia). Yuwen Tai's father Yuwen Gong (宇文肱) was known for his ability in battle. In 524, with Northern Wei's northern provinces overrun by agrarian rebels (the revolt of the Six Frontier Towns), Wuchuan was being held by one of the major rebels, Poliuhan Baling (破六韓拔陵). Yuwen Gong and another local leader, Heba Duba (賀拔度拔), ambushed Poliuhan's general Wei Kegu (衛可孤) and killed Wei, temporarily restoring order. It was probably at this time that Yuwen Tai met and befriended Heba Duba's son Heba Yue. Sometime after this incident, Yuwen Gong and his sons fled to Zhongshan (中山, in modern Baoding, Hebei), and were forced to join the army of another rebel general, Xianyu Xiuli (鮮于修禮). Yuwen Gong died in a battle between Xianyu's troops and Northern Wei troops, but Yuwen Tai continued to serve in Xianyu's troops. After Xianyu was killed by his general Yuan Hongye (元洪業) in 526, another Xianyu general, Ge Rong, in turn killed Yuan and took over Xianyu's troops, and Yuwen continued to serve Ge. However, he saw that Ge was not a competent leader and considered fleeing with his brothers, but before he could carry out his plans, Ge was defeated by the Northern Wei general Erzhu Rong in 528, and Erzhu forcibly moved Ge's troops to his power base at Jinyang (晉陽, in modern Taiyuan, Shanxi). Suspicious of the Yuwen brothers, Erzhu killed Yuwen Tai's older brother Yuwen Luosheng (宇文洛生), but Yuwen Tai pleaded his case with Erzhu and was spared.

In 529, the Northern Wei prince Yuan Hao, under support from the Liang dynasty, attacked Emperor Xiaozhuang and seized the capital Luoyang, declaring himself emperor. Emperor Xiaozhuang fled north of the Yellow River, and Erzhu advanced south to aid him, sending Heba Yue, who was then serving under Erzhu, to lead his forward troops. Heba made Yuwen Tai his assistant, and later on, after Erzhu defeated Yuan Hao, allowing Emperor Xiaozhuang to return to Luoyang, Yuwen was created the Viscount of Ningdu.

In 530, Erzhu Rong sent his nephew Erzhu Tianguang, with Heba and Houmochen Yue as assistants, to attack the rebel general Moqi Chounu, who then occupied the western provinces. Yuwen continued to serve under Heba. After Erzhu Tianguang defeated Moqi, Yuwen, who contributed in the campaign, was made the governor of Yuan Province (原州, roughly modern Guyuan, Ningxia), and he was said to have ruled the province with such kindness and faith that the people of the province proclaimed, "Had we had Governor Yuwen as our governor earlier, how would we have joined the rebellion?"

Late in 530, apprehensive that Erzhu Rong would eventually seize the throne, Emperor Xiaozhuang ambushed him and killed him in the palace. Subsequently, Erzhu Rong's clan members, led by his nephew Erzhu Zhao and cousin Erzhu Shilong, defeated and killed Emperor Xiaozhuang, first making Yuan Ye the Prince of Changguang emperor, and then further replaced Yuan Ye with Emperor Jiemin. In 531, the general Gao Huan rebelled against the Erzhus. Erzhu Tianguang was initially not particularly interested in aiding his Erzhu clan members, but felt compelled to, and he departed Chang'an to head east. While Erzhu Tianguang was away, Yuwen advised Heba to rise against the Erzhus, and Heba did, defeating Erzhu Tianguang's brother Erzhu Xianshou (爾朱顯壽), whom Yuwen subsequently captured, dividing control of the territory with Houmochen. By 532, Gao had defeated the Erzhus and seized power, deposing Emperor Jiemin and making Emperor Xiaowu emperor instead. When Gao subsequently tried to intimidate Heba into giving up his territory and reporting to Luoyang, but under the advice of Xue Xiaotong (薛孝通), Heba refused. He made Yuwen his lieutenant, and consulted him on most important matters. In 533, Yuwen volunteered to serve as messenger to Gao in order to observe Gao's abilities, and Heba agreed. When Gao met Yuwen, Gao was impressed by the answers Yuwen had to his questions and wanted to detain Yuwen, but Yuwen left Gao's domain before Gao could seize him. Subsequently, Heba sent Yuwen to confer with Emperor Xiaowu, who was not happy about Gao's hold on power, and Emperor Xiaowu and Heba were able to enter into a secret alliance against Gao. Heba made Yuwen the governor of the key Xia Province (夏州, roughly modern Yulin, Shaanxi).

By this point, Heba Yue, in alliance with Houmochen Yue, controlled almost all of the western provinces. However, one provincial governor, Cao Ni (曹泥), the governor of Ling Province (靈州, roughly modern Yinchuan, Ningxia), was aligned with Gao Huan and refused to follow Heba's orders. Heba Yue sent his assistant Zhao Gui to Xia Province to request Yuwen's opinions, and Yuwen, believing that Houmochen was unreliable, advised against an attack on Cao and suggested instead that Houmochen be attacked. Heba refused—not realizing that by this point, Gao's messengers had persuaded Houmochen to act against him. Heba and Houmochen rendezvoused at Gaoping (高平, in modern Guyuan, Ningxia), and then headed north against Cao—but as they advanced, Houmochen tricked Heba into coming to his camp for discussions, and then had his son-in-law Yuan Hongjing (元洪景) assassinate Heba. Initially, Heba's army was surprised and intimidated, but Houmochen, instead of taking over Heba's army, panicked and fled to Shuiluo (水洛, in modern Pingliang, Gansu), while Heba's army, without a central commander, withdrew to Pingliang (平涼, also in modern Pingliang). After some internal discussions, the army commanders decided to offer the command to Yuwen Tai, and they sent Du Shuozhou (杜朔周, later changed his name to Helian Da (赫連達)) to Xia Province to summon Yuwen Tai. Yuwen agreed, and Du and he quickly headed back toward Heba's army. (On the way, they encountered Gao's general Hou Jing, whom Gao had sent to try to take over Heba's army; Hou, surprised, withdrew to Gao's territory quickly.)

Emperor Xiaowu, hearing of Heba's death, sent Yuan Pi (元毗) to summon both Yuwen and Houmochen to Luoyang. Houmochen outright refused, and Yuwen persuaded Emperor Xiaowu to allow him to remain in command. Emperor Xiaowu agreed. Yuwen next sent a letter to Houmochen to rebuke him, and when Houmochen did not answer, prepared to launch an attack on Houmochen. He advanced quickly on Shuiluo, and Houmochen withdrew to Lüeyang (略陽, in modern Tianshui, Gansu), and then to Shanggui (上邽, also in modern Tianshui). He then further withdrew from Shanggui, and Shanggui surrendered to Yuwen. He decided to try to flee to Cao's territory, but on the way, believing that Yuwen's forces were close, committed suicide.

Gao Huan made an overture of alliance to Yuwen Tai, but Yuwen refused, instead arresting Gao's messengers and delivering them to Emperor Xiaowu. Emperor Xiaowu authorized him to take over Heba's authorities in the west and created him the Duke of Lüeyang.