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Abstract In this study, we conduct extensive high‐pressure experiments to investigate phase stability in the cobalt‐nitrogen system. Through a combination of synthesis in a laser‐heated diamond anvil cell, first‐principles calculations, Raman spectroscopy, and single‐crystal X‐ray diffraction, we establish the stability fields of known high‐pressure phases, hexagonal NiAs‐type CoN, and marcasite‐type CoN₂within the pressure range of 50–90 GPa. We synthesize and characterize previously unknown nitrides, Co₃N₂,Pnma‐CoN and two polynitrides, CoN₃and CoN₅, within the pressure range of 90–120 GPa. Both polynitrides exhibit novel types of polymeric nitrogen chains and networks. CoN₃feature branched‐type nitrogen trimers (N₃) and CoN₅show π‐bonded nitrogen chain. As the nitrogen content in the cobalt nitride increases, the CoN₆polyhedral frameworks transit from face‐sharing (in CoN) to edge‐sharing (in CoN₂and CoN₃), and finally to isolated (in CoN₅). Our study provides insights into the intricate interplay between structure evolution, bonding arrangements, and high‐pressure synthesis in polynitrides, expanding the knowledge for the development of advanced energy materials