Zhang Chengye (Chinese: 張承業) (846 – November 23, 922), né Kang (康), courtesy name Jiyuan (繼元), posthumous name Zhengxian (正憲), was a Chinese government official and eunuch. He originally served the Tang dynasty, but later became an important advisor to Former Jin princes Li Keyong and his successor Li Cunxu, who would later establish the Later Tang dynasty.

Zhang Chengye was born in 846, the year that Emperor Xuānzong of Tang took the throne. He was originally surnamed Kang, although it was not known whether he then carried the name of Chengye. He was from Tong Prefecture (同州, in modern Weinan, Shaanxi). He was castrated in his childhood, and he became an adoptive son of the eunuch Zhang Tai (張泰); he thus took the name of Zhang.

During the Guangqi era (885–888) of Emperor Xuānzong's grandson Emperor Xizong, Zhang Chengye became the overseer of Heyang Base (郃陽鎮, in modern Weinan), which was controlled by the eunuch-commanded Shence Armies. He was later recalled to the palace to be an attending eunuch. During the reign of Emperor Xizong's brother and successor Emperor Zhaozong, Zhang was frequently sent as an emissary to the major warlord Li Keyong the military governor of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi) and became friendly with Li Keyong. During Li Keyong's campaign against Wang Xingyu the military governor of Jingnan Circuit (靜難, headquartered in modern Xianyang, Shaanxi) and Li Maozhen the military governor of Fengxiang Circuit (鳳翔, headquartered in modern Baoji, Shaanxi) in 895 after Wang and Li Maozhen had marched on the imperial capital Chang'an and killed the chancellors Li Xi and Wei Zhaodu despite Emperor Zhaozong's protestations, Emperor Zhaozong had Zhang serve as the eunuch monitor of Li Keyong's army. After Li Keyong's victory over Wang later in the year, Zhang was made the director of the imperial winery. Subsequently, in 896, when Li Maozhen marched on Chang'an again and Emperor Zhaozong contemplated fleeing to Hedong, he sent Zhang to Hedong Circuit to serve permanently as eunuch monitor and to request Li Keyong to launch an army to save the imperial government. However, Emperor Zhaozong subsequently chose to flee to Zhenguo Circuit (鎮國, headquartered in modern Weinan), then-ruled by the military governor Han Jian instead. While Emperor Zhaozong was at Zhenguo's capital Hua Prefecture (華州), Zhang received a title as a general of the Left Shence Army.

Later, Li Keyong's military strengths were greatly decreased, and his archenemy Zhu Quanzhong the military governor of Xuanwu Circuit (宣武, headquartered in modern Kaifeng, Henan) was the strongest warlord of the land, such that Zhu was even able to put Hedong's capital Taiyuan Municipality under siege in 901 and nearly captured it. Zhu was allied with the chancellor Cui Yin, and in 901, when the powerful eunuchs at court, led by Han Quanhui, believed that Emperor Zhaozong and Cui were about to slaughter them, they seized Emperor Zhaozong and forcibly took him to Fengxiang, as they were allied with Li Maozhen. Zhu, at Cui's instigation, subsequently put Fengxiang's capital Fengxiang Municipality under siege. By 902, Fengxiang was in desperate straits, with the people resorting to cannibalism. Han had Emperor Zhaozong issue an edict calling for the regional governors to all attack Zhu, and Zhang, as the eunuch monitor of Hedong, advocated that Li Keyong launch an army to aid Fengxiang. Li Keyong agreed, but shortly after he launched his army in spring 903 to attack Jin Prefecture (晉州, in modern Linfen, Shanxi), he heard that Li Maozhen had already capitulated and turned the emperor over to Zhu, so he withdrew. Meanwhile, shortly after Li Maozhen turned over the emperor, Emperor Zhaozong, under the advocacy of Cui and Zhu, issued an edict ordering a general slaughter of all eunuchs. Li Keyong did not want to directly disobey the edict, but wanted to save Zhang, so he hid Zhang at Hulü Temple (斛律寺), while executing a condemned criminal in his stead. In 904, after Zhu had forcibly moved Emperor Zhaozong to the eastern capital Luoyang and then assassinated Emperor Zhaozong, Li Keyong publicly restored Zhang as the eunuch monitor.

In 907, Zhu Quanzhong forced Emperor Zhaozong’s successor Emperor Ai of Tang to yield the throne to him, ending Tang and starting a new Later Liang with him as its Emperor Taizu. Li Keyong, who then carried the Tang-bestowed title of Prince of Jin, refused to recognize the Later Liang emperor and continued to use the Tang era name of Tianyou, but became effectively the sovereign of his own state of Jin. (Li Maozhen, carrying the title of Prince of Qi, and Yang Wo, carrying the title of Prince of Hongnong (later known as Wu), were two other major regional warlords who also continued to use the Tang era name of Tianyou; another warlord, Wang Jian the Prince of Shu, soon claimed imperial title himself, establishing Former Shu.) Zhang Chengye, still using Tang-bestowed titles as well, continued to serve Li Keyong.

In spring 908, Li Keyong became gravely ill. He entrusted his son and heir Li Cunxu to his brother Li Kening, Zhang, officers Li Cunzhang (an adoptive son of Li Keyong's) and Wu Gong (吳珙), and secretary Lu Zhi (盧質), and then died. They supported Li Cunxu to succeed Li Keyong as the Prince of Jin and the military governor of Hedong. However, soon thereafter, Li Keyong's adoptive son Li Cunhao (李存顥) encouraged Li Kening, who was having policy disagreements with Zhang and Li Cunzhang, to seize the position for himself, and Li Kening agreed, planning to seize Li Cunxu and kill Zhang and Li Cunzhang, and then submit to Later Liang. When Li Cunxu found this out, he conferred with Zhang, Li Cunzhang, Wu, Li Cunjing (李存敬, another adoptive son of Li Keyong's), and Zhu Shouyin and formulated a plan to counter it. They preemptively arrested and executed Li Kening and Li Cunhao, affirming Li Cunxu's hold on the throne.

One decision Li Cunxu had to make immediately was how or whether to try to aid his cousin Li Sizhao the military governor of Zhaoyi Circuit (昭義, headquartered in modern Changzhi, Shanxi), who was then under siege at Zhaoyi's capital Lu Prefecture (潞州) by a large Later Liang army. Li Cunxu himself was intending on going to aid Li Sizhao himself, and Zhang supported him in this decision. Li Cunxu, in addition to gathering all of his own troops, also sent Zhang and Wang Jian (王緘, note not the same person as the Former Shu emperor) to Qi to seek Li Maozhen's aid. (Li Maozhen, however, lacked strengths to launch an aid army and therefore did not.) After the victory, Li Cunxu entrusted much of the governance of the circuit to Zhang, honoring him as an elder brother and often visiting his mansion to pay tribute to his mother.

Later in 908, Qi and Former Shu forces launched a joint attack on Later Liang, intending to capture Chang'an. Jin also launched an army, commanded by Zhang, to try to aid the Qi/Former Shu attack by diverting Later Liang forces. However, after the Later Liang generals Liu Zhijun and Wang Chongshi (王重師) defeated Qi troops, all three states withdrew.