King Helü of Wu 吳王闔閭 (r. 514-496 BCE), also written Helu 闔廬, personal name Ji Guang 姬光 and also called "Ducal Son" Gongzi Guang 公子光, was a ruler of the kingdom of Wu 吳 during the late Spring and Autumn period 春秋 (770-5th cent. BCE).
He was the son of King Zhufan 諸樊 (r. 560-548, or of King Yimei 夷眛 or Yumei 餘昧, r. 547-531). In 525 he commanded a campaign against the kingdom of Chu 楚 that ended in a defeat. He secretly planned to become king and prepared a plot against King Liao 僚 (r. 526-514 BCE), whom he had assassinated in 515.
In 506 Wu concluded an alliance with the states of Cai 蔡 and Tang 唐 for a war against Chu. In five battles, Wu obtained victory, and King Helü entered the capital of Chu, Ying 郢. Yet the king had soon to return because the armies of Qin 秦 approached to support the king of Chu, and because his own younger brother Fugai 夫槩 had proclaimed himself king of Wu. Fugai was forced into submission.
The victories against the armies of Chu continued in all subsequent battles. The King of Chu therefore shifted his capital to Ruo 鄀 (modern Yicheng 宜城, Hubei) located farther to the west.
In 496 King Helü also attacked the state of Yue 越 and was defeated at Suili 檇李 (modern Jiaxi 嘉西, Zhejiang). During the battle he was injured by a halberd and died not long thereafter.