Zhou Ji (Chinese: 周岌) was a Chinese warlord of the late Tang Dynasty who seized control of Zhongwu Circuit (忠武, headquartered in modern Xuchang, Henan) in 880, briefly submitted to the agrarian rebel Huang Chao's new state of Qi, and later returned the Tang fold, controlling Zhongwu until he was forced to abandon it in 884 due to an attack by Lu Yanhong. Lu might have killed him subsequently.
Little is known about Zhou Ji's background, as he did not have a biography in either of the official histories of Tang Dynasty, the Old Book of Tang and the New Book of Tang. As of 880, he was serving as an officer of Zhongwu Circuit, under the military governor Xue Neng (薛能). In late 880, as part of the Tang operations to stop the northwestward advancement of the major agrarian rebel Huang Chao, many circuits in the east were ordered to send troops to Yin River (溵水, a major branch of the Shaying River). Xue sent Zhou with Zhongwu troops there. Before Zhou got there, however, there was a disturbance at Zhongwu's capital Xu Prefecture — as the soldiers from Ganhua Circuit (感化, headquartered in modern Xuzhou, Jiangsu), who were undisciplined but whom Xue thought he could control (as he had previously been the military governor of Ganhua), after Xue welcomed them into the city, were instead rioting and demanding various supplies. Zhou heard about the disturbance and returned to Xu Prefecture with his troops. He then attacked the Ganhua troops and slaughtered them. Further, resenting Xue for treating the Ganhua soldiers well, he expelled Xue. Xue tried to flee to Xiangyang, but mutineer soldiers under Zhou chased him down and slaughtered him and his family. Zhou claimed the title of acting military governor. As a result of Zhou's mutiny, Qi Kerang the military governor of Taining Circuit (泰寧, headquartered in modern Jining, Shandong), feared that Zhou would ambush him, and thus abandoned his position at Ru Prefecture (汝州, in modern Pingdingshan, Henan) and returned to Taining, causing the various circuits' troops gathered at Yin River to also abandon their positions. This allowed Huang an open path to the Tang imperial capital Luoyang. Faced with the Huang threat, the imperial government was unable to act against Zhou and almost immediately commissioned him as the military governor of Zhongwu. Huang was thereafter able to capture both Luoyang and the imperial capital Chang'an, forcing then-reigning Emperor Xizong to flee to Chengdu. Meanwhile, the Zhongwu officer Qin Zongquan, whom Xue had previously sent to help defend Cai Prefecture (蔡州, in modern Zhumadian, Henan), seized the prefecture. Zhou was himself unable to control Qin and therefore made him the prefect of Cai Prefecture.