Kang Sheng (Chinese: 康生) (1898–December 16, 1975), Communist Party of China (CPC) official, was the head of the People's Republic of China's security and intelligence apparatus at various points until his death, and was subsequently accused along with the Gang of Four of being responsible for persecutions during the Cultural Revolution.

Kang was born as Zhang Zongke into a wealthy landlord family in Jiaonan, Shandong Province. He joined the Communist Party in 1925 in Shanghai, where he worked as a labor organizer province with different alias such as Zhang Shaoqing and Zhao Rong, and took part in the unsuccessful Communist uprising in 1927, holding the position of Secretary of Shanghai Labor Union, Commissioner, Secretary General and Minister of Organization Department of the CPC Jiangsu Province division. In 1930 Kang was elected as the Minister of Organization Department and Censor Commissioner of Central Committee of CPC in the Third Plenary Meeting of the Sixth National Congress of CPC, which meant that Kang had risen to prominence within the CPC and that he began his career as the CPC's secret police chief, working with Li Kenong and Chen Geng, directly under Zhou Enlai. Li was mainly responsible for decoding; Kang was in charge of operations; Chen Geng was in charge of a death squad, executing communist traitors and protecting important communist leaders.

When the uprising was put down by Kuomintang, Kang escaped from Shanghai and joined the surviving Communist cadres in the rural areas. He was sent to Moscow in 1933 as the delegate of CPC in Comintern and spent some time studying Soviet security and intelligence techniques. In Moscow, Kang became acquainted with Wang Ming, a pro-Soviet CPC leader. In 1934 Kang was elected as member of Politburo and Commissioner of Central Committee of CPC. With the support of Wang Ming and his mentors in Moscow, Kang honed his Stalinist methods of persecution by purging members of the CPC and the Chinese community working and studying in Moscow. He labeled many of them Trotskyists and threw them into the the gulag; he even executed a few.

In 1935, under the name Kang Sheng, he returned to Mao Zedong's base at Yan'an (Yenan). In Moscow, Kang had already realized that Wang Ming was falling out of Moscow's favor, and Zhang Guotao was originally selected by the Comintern to replace Wang. Kang Sheng defected immediately from Wang's camp, but he was very clever politically and instead of directly siding with Zhang Guotao to fight both Wang Ming and Mao Zedong, he allied himself with Mao to destroy Wang's faction within the communist party, seeing Wang as the greatest enemy at the time. After Kang Sheng's death, the Chinese communist regime accused him of planning to use Mao's power and influence to defeat Wang's faction first and once Mao's camp was weakened in the struggle against Wang's camp, Kang Sheng would then show his true colors by supporting Zhang Guotao. Whatever the validity of this accusation, Kang Sheng did not have the opportunity to prove this accusation bestowed on him after his death: although Wang Ming's faction was successfully purged, Zhang Guotao's power and influence diminished to nearly zero as well: around a year later, Zhang's remaining force, which was the largest among the Chinese Red Army, was completely annihilated by the Ma clique of the nationalist warlords in 1936. Kang Sheng immediately joined Mao's camp; since he appeared only involved in fighting Wang Ming's faction but not openly provide direct support Zhang Guotao's camp, Mao reward Kang as the head of the so-called Social Affairs Department, the Party's chief security service, which he headed until 1949.

In order to completely eliminate Wang Ming's and Zhang Guotao's power bases and allies in CPC, Mao and Kang launched the "Zheng Feng" in 1942. Although it was ostensibly a campaign only to ensure political conformity with Mao Zedong Thought, mainly through ideological criticism and self-criticism, it evolved into a vicious campaign of physical and psychological persecution of real or imagined dissidents. At one point the number of victims was so large that fierce resistance had accumulated against Mao's authority, threatening his position of supremacy within the movement. Kang was eventually compelled to shoulder the blame for his crimes and to make apologies for his excesses in public, after which he kept a low profile in the years to follow. On the other hand, after the Stalinist campaigns executed and overseen by Kang, the KMT discovered that it was quite difficult to infiltrate the CPC’s camp and to obtain valuable intelligence about the CPC as it had done effectively in the 1930s when the CPC operated in major cities such as Shanghai. Kang employed "red terror" tactics in Yan'an, turning it into a closed empire, and greatly improved the efficiency with which Mao’s orders were carried out, which contributed to the CPC’s victory, as compared with the KMT’s inefficient methods of policy execution.

During the 1946-49 Chinese Civil War, Kang was demoted to CPC chief in Shandong Province and appointed only as Second Vice General Secretary of the East China Bureau of the CPC, in which he carried out the land reform movement with a zeal that led him to encourage the murder of many landlords in Shanxi and Shandong Provinces.

At Yan'an, Kang became a close friend of Jiang Qing, who may have been Kang's maid during his youth in Shandong, and who became a second-rate young actress in Shanghai and a newly converted Communist. He introduced her to Mao Zedong, who later married her. Before Mao and Jiang's marriage, Kang abused his power of censorship to conceal Jiang's arrest by and confession to the Kuomintang in Shanghai, which might have impeded the marriage and altered the course of China's modern history. This favor, along with his role in the security apparatus, made Kang one of the most intimate figures in the Party of Mao and served to save Kang from time to time.

Kang played no visible public role in the early years of the PRC: it is said that the enmity of President Liu Shaoqi and Premier Zhou Enlai kept his role to a minimum. He resurfaced in the mid- 1950s following his active role in the purge of military leader Peng Dehuai, and apparently resumed control of the CPC security apparatus. He became Mao's personal agent in the intra-Party struggles that began with the "Anti-Rightist Campaign" of 1959 and culminated in the 1966-76 Cultural Revolution. As a close associate of Jiang Qing, he became a member of the Party Secretariat under Deng Xiaoping in 1962. By 1966, he became an "adviser" to the Cultural Revolution Group under the Central Committee, and a member of the Politburo's Standing Committee. His actions set into motion the Cultural Revolution, which he created in order to increase his personal power and rank within the CPC.

Kang was closely involved in the Cultural Revolution purges which resulted in the downfall of Peng Dehuai, Liu Shaoqi, Deng Xiaoping, Marshal Lin Biao, Marshal He Long, and many other leading CPC figures. His position in the CPC rose with the fall of each of these high-ranking leaders. Kang's campaigns of state terror reached as far as Inner Mongolia, where he instigated a deadly witchhunt for members of the defunct Inner Mongolian People's Party, which had once existed as a separatist party but was disbanded and absorbed by the CPC long before; and Yunnan Province, where thousands were died. In this wave of persecution, Kang Sheng adopted a different tactics than that of Yan'an: learning from his dismay from Zheng Feng movement more than two decades earlier, Kang Sheng cleverly stayed in the background this time, and encouraged the Red Guards (China) and the general populace to eliminate the class enemy, as well as fighting each other, hence shifted the responsibility ostensively away from himself and Mao. As a result, Mao was pleasd with Kang Sheng for achieving the elimination of the so-called class enemy while shifting the responsibility to others (including those already died in the infights between different sects of Red Guards (China)), and Kang Sheng's position was further strengthened in the Cultural Revolution.

Kang also left a lasting imprint on China's foreign policy. While the mainstream of the CPC leadership cultivated Prince Norodom Sihanouk as Cambodia's anti-Western and anti-imperialist leader, Kang advocated that Khmer Rouge guerrilla leader Pol Pot was the real revolutionary leader in the Southeast Asian nation. As a result, Pol became the recipient of Chinese aid for years to come.

At the apex of his power, Kang ranked fourth behind Mao, Lin Biao, and Zhou Enlai. His last service to Mao was the 1976 campaign to criticise "rightist deviationism," which was aimed at Zhou Enlai and Deng Xiaoping, though Kang died of cancer in late 1975 before it was launched. Even before drawing his last breath, Kang had called Mao's English interpreters and proteges Nancy Tang and Wang Hairong to his hospital, accusing Jiang Qing of having betrayed the CPC to the KMT before the Communist victory. Kang may have forecasted Jiang's fall, or he may merely have been speculating as to her fate.

Had Kang not died, he would certainly have been removed from power along with the Gang of Four (Jiang Qing and her associates) after Mao's death. In a secret speech delivered in 1978, Hu Yaobang (who became CPC General Secretary in 1981) compared Kang to Soviet secret police chiefs Felix Dzerzhinsky and Lavrenty Beria. He was posthumously expelled from the Party in 1980, and his remains were removed from Babaoshan Revolutionary Cemetery in Beijing, where the remains of many prominent CPC leaders are interred.

In contrast to Dzerzhinsky, who was a pious believer in communism and who lived a very simple and modest daily life, Kang lived an extravagant and corrupt lifestyle. As the best calligraphist among senior leaders of CPC, as well as a painter, art and antique connoisseur, poet, and historian, Kang had a great appetite for valuable Chinese antiques and used his power to embezzle many from the Forbidden City and from the storehouses of the Cultural Relics Bureau during the Cultural Revolution, a fact uncovered only after his death. According to the audits by the Chinese government and researches by the Japanese, Kang Sheng was both the very first millionaire and the first multi-millionaire in China, based on the value of artifacts he owned (or more precisely, robbed and stole) in 1970s price. Furthermore, it was rumored that he had kept an affair with the sister of his wife Cao Yi'ou for quite a long time, and he built several villas for their rendezvous.

Kang's career is covered in the book ISBN 0-688-09722-7 The Chinese Secret Service by Roger Faligot and Remi Kauffer