In China, the word hanjian (traditional Chinese: 漢奸; simplified Chinese: 汉奸; pinyin: Hànjiān; Wade–Giles: han-chien) is a pejorative term for those seen as traitors to the Chinese state and, to a lesser extent, Han Chinese ethnicity. The word hanjian is distinct from the general word for traitor, which could be used for any country or ethnicity. As a Chinese term, it is a digraph of the Chinese characters for "Han" and "traitor". Han is the majority ethnic group in China; and Jian, in Chinese legal language, primarily referred to illicit sex. Implied by this term was a Han Chinese carrying on an illicit relationship with the enemy. Hanjian is often worded as "collaborator" in the West.

The term hanjian emerged from a "conflation of political and ethnic identities, which was often blurred in the expression of Chinese nationalism." It is a label applied to individuals who are designated collaborators and by which were not all ethnically Han. The modern usage of the term stems from the Second Sino-Japanese War in which circumstances forced political figures in China to choose between resistance and collaboration. The nuance in understanding why Chinese individuals would decide to cooperate with the Japanese obscures the seemingly clear-cut definition of hanjian, evolving it into an ambiguous term in modern history.

When observing the era of the Sino-Japanese War, there tends to be two types of hanjian: the educated and intellectuals, who "simply wanted to get power and wealth for themselves"; and the poor and uneducated, whose poverty drove them to collaborate and whose "ignorance saved them from even thinking they had to justify what they were doing". Due to this notion and the modern ambiguity of the term, each of these two categories had various motives with the majority being different but some overlapping.

Educated hanjian is often reserved for those who were either scholars or within government. The most infamous hanjian government in mainland China is the Reorganized National Government of the Republic of China, often referred to as the Wang Jingwei regime after Wang Jingwei, its president. The Wang Jingwei regime sought to be the dominant governmental force in China and believed it could do so by collaborating and being submissive to Japan in what they deemed as their "Peace Movement". Wang experienced resistance to his government when he visited Shanghai, among other cities. It was recorded that "intellectuals who showed sympathy for Wang risked ostracism, if not death."

During the Second Sino-Japanese War, the National Revolutionary Army was defeated in various battles by the Imperial Japanese Army. Chiang Kai-shek explained that hanjian espionage helped the Japanese. He ordered CC Clique commander Chen Lifu to arrest the hanjians. 4,000 were arrested in Shanghai and 2,000 in Nanjing. Because martial law was enforced, formal trials were not necessary, and the condemned were executed swiftly, while thousands of men, women and children watched with evident approval.

Taiwanese soldiers who fought in the Japanese military against Chinese forces and the Allies are also considered to be hanjian. The Republic of China issued an important law in 1937:

The centerpiece of anti-hanjian laws, "Regulations on Handling Hanjian Cases (處理漢奸案件條例; 处理汉奸案件条例; Chŭlǐ Hànjiān Ànjiàn Tiáolì)", promulgated in August 1937, identified collaborators based on their wartime conduct and stipulated punishments regardless of their age, gender, or ethnicity. Popular anti-hanjian discourse, however, paid particular attention to "female collaborators" and deployed a highly gendered vocabulary to attack hanjian suspects of both sexes. Complementing the legal purge of collaborators, such literature brought extreme pressure on individuals targeted as hanjian and influenced how political crimes should be exposed and transposed onto other aspects of social life.

Several Taiwanese were prosecuted by the Nationalist government as hanjian, despite a Judicial Yuan interpretation issued in January 1946 that advised against such action.