Yi Eok-gi (Hangul/Hanja: 이억기/李億祺; Born: September 3rd 1561 in Seoul-Hanseong – Killed in Action: August 27th 1597 in Chilcheollyang Strait, present-day Tongyeong City, Southern Gyeongsang Province) was the commander of the Eastern Jeolla Fleet and later became the commander of Western Jeolla Fleet. He was one of Yi Sunshin's good friends during the Japanese Imjin Invasions.
Yi Eok-gi is a distant relation to the Royal House of Jeonju Yi. He is 5th Generation of Grand Prince Yangnyeong Yi Je, elder brother of King Sejong the Great a.k.a Grand Prince Chungnyeong Yi Do.
He was eventually killed in the devastating Battle of Chilcheollyang Strait while assisting Won Gyun, the Naval Commander of the entire Korean navy at that time. Won Gyun and Yi Eok-gi were forced to retreat multiple times back, being crushed by the advancing Japanese navy, and finally landed ashore on a nearby island (Hansan-do) with a few survivors.
However, a fort filled with Japanese Soldiers on the island were waiting for them, and killed every person there. Yi Eok-gi met his end on this island. At the same time, Joseonese Naval Base in Hansan-do was vulnerable to Japanese forces and completely destroyed.
The attack order for the Battle of Chilcheollyang originated from the King Seonjo himself and the lack of aggressive action taken by Admiral Won. It should be also noted he was awarded lesser degree of honor than Won Gyun due to political reasons. The final flagship of Chang Bogo U209-class Submarine, SS-071 ROKS Yi Eok-gi was commissioned in 2001 in honor to the fallen admiral.