Xu Zhanzhi 徐湛之 (410-453), courtesy name Xiaoyuan 孝源, from Tan 郯 in the commandery of Donghai 東海 (today's Tancheng 郯城, Shandong), was a high official of the Liu-Song dynasty 劉宋 (420-479), one of the Southern Dynasties 南朝 (420-589).
Xu's mother was a daughter of the dynastic founder Liu Yu 劉裕 (363-422; Emperor Wu 宋武帝, r. 420-422). In 422, he was invested as District Marquis of Zhijiang 枝江縣侯. In 429, he was made Librarian of the Heir Apparent (taizi xima 太子洗馬), and then appointed erudite in the Directorate of Eduation (guozi boshi 國子博士), General Fighting with Authority (fenwei jiangjun 奮威將軍), governor (taishou 太守) of the commandery of Nanpengcheng 南彭城, then of Peijun 沛郡, later Gentleman Attendant of the Palace Gate (huangmen shilang 黃門侍郎), Director of the Palace Library (mishujian 秘書監), General of the Right Army (youjun jiangjun 右軍將軍), palace attendant (shizhong 侍中), General of the Imperial Guard (xiaoji jiangjun 驍騎將軍) and Cavalier Attendant-in-ordinary (sanji changshi 散騎常侍).
Xu was involved in the plot of Liu Zhan 劉湛 to kill the emperor and enthrone Liu Yikang 劉義康 (409-451), the Prince of Pengcheng 彭城, but he was spared capital punishment because his mother, the Princess of Guiji 會稽公主, beseeched Emperor Wen 文皇帝 (r. 424-453) to pardon him. He was dismissed, but later returned into public service as General Commanding the Troops (guanjun jiangjun 冠軍將軍), metropolitan magistrate (yin 尹) of Danyang 丹陽 and General Attacking the Barbarians (zhenglu jiangjun 征虜將軍). He was promoted to Director of the Palace Secretariat (zhongshu ling 中書令), Supervisor of the Household of the Heir Apparent (taizi zhanshi 太子詹事), General of the Front Army (qianjun jiangjun 前軍將軍), regional inspector (cishi 刺史) of the province of Nanyanzhou 南兗州, Vice Director of the Imperial Secretariat (shangshu puye 尚書僕射) and Protector-General (hujun jiangjun 護軍將軍). In 453, when Liu Shao 劉劭 assassinated Emperor Wen, Xu Zhanzhi was also killed.
Emperor Xiaowu 孝武帝 posthumously granted him the honorific title of Minister of Works (sikong 司空). His posthumous title is Duke Zhonglie 枝江忠烈公.