Wu was a state during the Spring and Autumn Period in China. The state of Wu straddled the mouth of the Chang Jiang river east of the State of Chu. Considered a semi-barbarian state by ancient Chinese historians, its capital was Suzhou.

The State of Jin aided Wu's rise to power as a useful ally against the State of Chu. In 584 BC, Wu invaded the State of Yan and rebelled against the State of Chu; the later action occurred after being persuaded by Wuchen, a minister of the State of Jin who defected from Chu.

Afterwards, Wu would be a constant threat to the state of Chu on its southeastern flank until its demise. Wu curried relationships with Chu's vassals in the Chang Jiang river region to weaken support for Chu. In 506 BC, Wu launched a surprise attack and occupied the capital of Chu. Afterwards, Wu was briefly the most powerful nation, and turned to other campaigns, defeating the State of Qi in 484 BC.

Ironically, Wu was later threatened by an upstart state to its south, the State of Yue; the State of Chu aided Yue's rise to power as a counter to Wu. Although Wu won a major victory against Yue in 494 BC, it failed to completely subjugate Yue, helped in part by Yue's bribing of an important Wu minister. While Wu was engaged in a military campaign in the north, Yue launched a surprise attack on Wu in 482 BC and conquered the capital. Eventually, the State of Yue conquered Wu in 473 BC.