Okjeo, an ancient Korean tribal state, existed in the northern Korean peninsula from potentially the 2nd century BCE to the 5th century CE. It was divided into two main regions: Dong-okjeo (Eastern Okjeo), covering the area of present-day Hamgyŏng provinces in North Korea, and Buk-okjeo (Northern Okjeo), located around the Duman River region. While Dong-okjeo was often simply referred to as Okjeo, Buk-okjeo had alternate names such as Chiguru or Guru, with the latter also being a name for Goguryeo.^[32] Okjeo neighbored the minor state of Dongye to its south and had a history interwoven with larger neighboring powers like Gojoseon, Goguryeo, and various Chinese commanderies.^[33]

Throughout its existence, Okjeo experienced alternating periods of dominance by Chinese commanderies and Goguryeo. From the 3rd century BCE to 108 BCE, it was under Gojoseon's control. By 107 BCE, the Xuantu Commandery exerted its influence over Okjeo. Later, as Goguryeo expanded, Okjeo became part of the eastern Lelang Commandery. The state, due to its strategic location, frequently served as a refuge for neighboring kingdoms; for instance, Goguryeo's King Dongcheon and the Buyeo court sought shelter in Okjeo during invasions in 244 and 285, respectively. However, by the early 5th century, Gwanggaeto the Great of Goguryeo had fully conquered Okjeo.

Cultural information about Okjeo, though sparse, suggests that its people and practices bore resemblances to those of Goguryeo. The "Samguk Sagi" describes Eastern Okjeo as a fertile land nestled between the sea and mountains, and its inhabitants as brave and skilled foot soldiers. Their lifestyle, language, and customs—including arranged marriages and burial practices—shared similarities with Goguryeo. The Okjeo people interred family members in a single coffin and had child-brides live with their groom's family until reaching adulthood.