The xia (俠) is a righteous person who excels in personal combat and may use their armed expertise to right social unfairness or injustice (鋤強扶弱). Xia could be roughly compared to "chivalry" and identified with the Western concept of knights and knighthood, although they are not strictly interchangeable. The feudalist overtones are wholly missing from the Chinese concept; unlike a knight, the xia ("chivalrous man") need not serve a lord or hold any military power; neither are they required to be from an aristocratic class. Nor does the notion of "xia" correspond to the Japanese samurai code of bushido. The main identification of a xia is a code of conduct and an ideology of honor and social justice dedicated to serving the good of the people.

A good description comes from Sima Qian:

He will surely honor his words; he will definitely carry out his actions. Whatever he promises he will fulfil. He does not care his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, nor shamelessly extol his own virtues.

The concept of xia goes back to the Zhou dynasty and the Spring and Autumn period. Referring to a class of warriors (the shi 士) whose social position is sandwiched between the commoners and the royalties, the xia (sometimes known as xiake 俠客 or xiashi 俠士) is originally the military counterpart (wu-shi 武士) of the more scholarly shi (仕) who eventually developed into Confucian scholars. Both are highly prized by feudal princes and warlords, one becoming intellectual advisors who contribute to the governing of the state, the other ending up as guest residents of their masters living by the blade. In ancient China, their preference to use force to resolve a conflict sometimes made them unpopular and inseparable from the common ruffians in the eyes of bureaucrats. The Legalist Han Feizi, for example, listed the xia among the five vermins of society.

The concept of xia however underwent many transformations through the centuries. By the end of the Qing dynasty it has come to represent an ideal hero who wielded power by force, but could withhold it if necessary, and more importantly, possesses a sense of moral justice.

A close equivalence of xia to the English world can be found in Robin Hood, frequently identified by the Chinese as a "xia-robber" (俠盜) -- one with his own morally justifiable code of conduct despite being a law-breaker. Batman is also called a xia in Chinese translation.

Xia is the basis for the Wuxia genre of Chinese literature and cinema.