Dingjunshan (Mount Dingjun) is a mountain in Mian County, within the Hanzhong municipality of Shaanxi Province, China. It lies across from Tiandang Mountain, from which it is separated by the Han River, and it stands near the old Yangping Pass.
The mountain is located in the southwestern part of Shaanxi, in the Han River valley region around Hanzhong. Its position near the Han River and the historic Yangping Pass places it within a corridor that has long served as a route between the Wei River valley to the north and the Sichuan basin to the south.
Dingjunshan is chiefly known for its association with the Three Kingdoms period of Chinese history, when the area around Yangping Pass and the Han River was of strategic importance. The mountain's setting, facing Tiandang Mountain across the river, is its defining geographic feature.