Emperor Jianwen of Liang (梁簡文帝; 2 December 503 – 551), personal name Xiao Gang (蕭綱), courtesy name Shizuan (世纘), childhood name Liutong (六通), was an emperor of the Chinese Liang Dynasty. He was initially not the crown prince of his father Emperor Wu, the founder of the dynasty, but became the crown prince in August 531 after his older brother Xiao Tong died. In 549, the rebellious general Hou Jing captured the capital Jiankang, and Hou subsequently held both Emperor Wu and Crown Prince Gang under his power, having Crown Prince Gang take the throne (as Emperor Jianwen) after Emperor Wu's death later that year. During Emperor Jianwen's reign, he was almost completely under Hou's control, and in 551, Hou, planning to take the throne himself, first forced Emperor Jianwen to yield the throne to his grandnephew Xiao Dong the Prince of Yuzhang, and then sent messengers to suffocate the former emperor.

Xiao Gang was born in 503, as the third son of Emperor Wu. His mother Consort Ding Lingguang (丁令光) also gave birth to Emperor Wu's firstborn son and crown prince Xiao Tong, and therefore carried a special status within his palace even though she was never empress. In 506, at the age of three, Xiao Gang was made the Prince of Jin'an. As he grew in age, he was given a number of progressively higher offices. In January 527, when Consort Ding died, he resigned those offices to observe a mourning period for her, but Emperor Wu restored him to those offices before the mourning period was over.

Consort Ding's death would bring about a disastrous effect in the relationship between Xiao Gang's father Emperor Wu and Xiao Gang's brother Xiao Tong. Xiao Tong sought out an appropriate place to bury Consort Ding, but while he was doing so, a land owner bribed the eunuch Yu Sanfu (俞三副) into convincing Emperor Wu that that piece of land would bring good fortune for the emperor, and so Emperor Wu bought the land and buried Consort Ding there. However, once Consort Ding was buried, a Taoist monk informed Xiao Tong that he believed that the land would bring ill fortune for Consort Ding's oldest son—Xiao Tong. Xiao Tong therefore allowed the monk to bury a few items intended to dissolve the ill fortune, such as wax ducks, at the position reserved for the oldest son. Later on, when one of Xiao Tong's attendants, Bao Miaozhi (鮑邈之), was squeezed out of Xiao Tong's inner circles by another attendant, Wei Ya (魏雅), he, in resentment, reported to Emperor Wu that Wei had carried out sorcery on Xiao Tong's behalf. When Emperor Wu investigated, waxed ducks were found, and Emperor Wu became surprised and angry, and wanted to investigate further. He only stopped the investigation when he was advised to do so by the prime minister Xu Mian, executing only the Taoist monk who had suggested the burial of wax ducks. Xiao Tong became humiliated in the affair, and was never able to clear himself completely in his father's eyes.

Xiao Tong died in May 531. Under Confucian rules of succession, his oldest son Xiao Huan (蕭歡) the Duke of Huarong was expected to succeed him as crown prince, and Emperor Wu summoned Xiao Huan back to the capital Jiankang in order to do so. However, still resentful over the wax duck affair, he hesitated for weeks without carrying out the creation, and finally did not do so. Instead, against popular opinion, he installed Xiao Gang, his then-surviving oldest son, as crown prince on 5 August 531. Xiao Gang's staff advisor Zhou Hongzheng (周弘正) wrote a memo to Xiao Gang advising him to decline, but Xiao Gang did not do so, although he subsequently avenged Xiao Tong's disgrace by executing Bao Miaozhi.

As crown prince, Xiao Gang was a distinguished poet, as well as patron of the poets Yu Jianwu and Xu Chi (徐摛), as well as Xu Ling, the anthologist of New Songs from the Jade Terrace. The poets Yu Jianwu and Xu Chi's writing style influenced Xiao Gang greatly. It became known as the "Xu-Yu Style" or the "Palace Style", with "palace" referring to the Eastern Palace, the official residence of the heir apparent. Initially, Emperor Wu was displeased about this development, but once Emperor Wu met Xu, he was impressed by Xu's talents.

As Crown Prince and "Assistant Monarch," Xiao Gang carried out much decision-making duties in the imperial administration. As Emperor Wu aged, Xiao Gang's younger brothers Xiao Xu (蕭續) the Prince of Luling, Xiao Guan (蕭綸) the Prince of Shaoling, Xiao Yi the Prince of Xiangdong, and Xiao Ji the Prince of Wuling grew less obedient of his edicts, and effectively exercised imperial powers in their provincial domains. Fearing that his brothers would seize power, Xiao Gang selected elite troops to be the palace guards for the crown prince's palace.

In 547, the Eastern Wei general Hou Jing, in a conflict with the new regent Gao Cheng, surrendered the 13 provinces (the region between the Yellow River and the Huai River) to Liang, seeking aid from Liang. However, both Xiao Gang's cousin Xiao Yuanming the Marquess of Zhenyang, and Hou himself, were defeated by the Eastern Wei general Murong Shaozong. Xiao Yuanming was captured, while Hou fled and, surprising the Liang governor of Southern Yu Province (南豫州, modern central Anhui), Wei An (韋黯), seized the key city Shouyang (壽陽, in modern Lu'an, Anhui), the capital of Southern Yu Province. Instead of punishing Hou, however, Emperor Wu allowed him to serve as the governor of Southern Yu Province. It is unclear whether Xiao Gang was involved in making these decisions, but he was clearly informed about them, as he revealed these decisions to his assistant He Jingrong (何敬容).

Soon, however, Hou, believing that Emperor Wu, who engaged in peace talks with Eastern Wei and appeared to be willing to betray him to exchange for Xiao Yuanming, rebelled in summer 548. Hou's army quickly advanced on Jiankang, assisted by Xiao Gang's cousin Xiao Zhengde the Prince of Linhe, putting Jiankang under siege. Emperor Wu put Xiao Gang in charge of the defenses, but Xiao Gang was unsuccessful in preventing the outer city from falling. The imperial troops were forced to withdraw into the palace. When Hou then claimed that it was the corrupt official Zhu Yi that he wanted to kill, Xiao Gang confirmed that Zhu was indeed corrupt, but advised against executing Zhu in that it would serve nothing in the campaign against Hou. Soon, Hou declared Xiao Zhengde emperor. While provincial troops gathered near Jiankang to try to relieve the besieged palace, those troops, commanded by Liu Zhongli (柳仲禮) and Xiao Guan, were unsuccessful, and ultimately, after Liu was nearly killed in a battle, Liu refused to engage Hou any further, leaving the palace troops to fend for themselves. (Xiao Yi and Xiao Ji, although they each had large numbers of troops in their domains, largely stood and sent only token troops.) In winter 548, Hou's general Fan Taobang (范桃棒) offered to rebel against Hou, and while Emperor Wu was initially in favor of the idea, Xiao Gang spoke against it, and it was not carried out. Soon, Fan was killed by Hou, and an opportunity was lost.