The 1st Marine Infantry Division (Korean: 제1해병사단; Hanja: 第1海兵師團), also known as Sea Dragon Division (Korean: 해룡부대; Hanja: 海龍部隊), is an infantry division of the Republic of Korea Marine Corps.

In September, before the Inchon Landing, ROKMC regiment size unit was formed and attached to USMC 1st Marine Division.

At that time, 1st Marine Division called this unit as the ROKMC 1st Marine Regiment for convenience' sake.

On 20 December 1950, ROKMC 1st Marine Regiment was founded and this regiment is one of the parent organization of 1st Marine Division[1] On 1 February 1954, reorganized into as the ROKMC 1st Marine Brigade.

[citation needed] On 15 January 1955, reorganized into as the ROKMC 1st Marine Division.