Ganjiakou Subdistrict () is a subdistrict of Haidian District, Beijing, It borders Zizhuyuan and Beixiaguan Subdistricts in the north, Zhanlanlu and Yuetan Subdistrict in the east, Yangfangdian Subdistrict in the south, and Balizhuang Subdistrict in the west. As of 2020, its population was 117,946.
The name Ganjiakou () came from a village that used to exist within the region.
Ganjiakou Subdistrict was divided into 24 communities as of 2021: