| Hangul: | 개루왕 |
| Hanja: | 蓋婁王 |
| Rr: | Gaeru-wang |
| Mr: | Kaeru-wang |
Gaeru of Baekje (died 166, r. 128–166) was the fourth king of Baekje, one of the Three Kingdoms of Korea.
According to the history compilation Samguk Sagi, he was the son of the previous king Giru. He became king upon Giru's death in 128 which was the 52nd year of his reign. The Samguk Sagi records that "his character was respectful and also orderly in his conduct".[1]
In 132, he founded Bukhansanseong in present-day Goyang city, Gyeonggi, South Korea. Baekje fought off many Goguryeo (the northern Korean kingdom) invasions from this fortress, and the 5th king Chogo based his northward campaign on it. Baekje's relationship with the southeastern rival Silla was peaceful for most of his period of reign. However, in 145, a Silla minister named Gilseon failed his coup d'etat attempt and fled to Baekje. Gaeru gave him refuge despite the Silla king Adalla's written request for his return. Silla subsequently attacked Baekje, and a broad war over the Sobaek Mountains ensued.
Samguk Sagi:
During the Spring and Autumn period, when Pu of Chu fled to Lu, Ji Wenzi said, "Seeing one who conducts himself properly toward his lord is like seeing a child who is filial to its father and mother. Upon seeing one who is not proper to his lord, he should be killed like a hawk on a sparrow. Seeing Pu of Chu, [he said that] he has no measure of virtue and had murderous ethics, and this passed. Now Gilseon was also a wicked and rebellious man, and the king of Baekje took him in and hid him. Thus we can say that concealing a villain makes one a harborer. Therefore, the peace was lost with neighboring countries, and the king made his people suffer under the burden of attack. This lacked insight.[2]
The Samguk Sagi states that Gaeru's eldest son became the 5th king Chogo and the second son became the 8th king Goi. This chronological inconsistency is thought to indicate a power struggle between two royal lines. The 21st king Gaero (also known as Geungaeru) apparently took Gaeru's name to assert the legitimacy of this.