Cai Hesen (March 30, 1895 – August 4, 1931) was an early leader of the Chinese Communist Party (CCP), and a friend and comrade of Mao Zedong.

[2] In April 1918, Cai, Mao Zedong, and a dozen others organized the New People's Study Society (Xin Min Xue Hui) in Changsha.

Yang Changji had urged his students to stay away from holding public office and to serve society by maintaining independence and moral purity.

When he heard that the anarchists and educators Cai Yuanpei and Li Shizeng had organized a Work-Study Program to send students to France who would finance their study by working in French factories, he and other members of the Society went to Beijing to seek their help.

At a time when "free love," that is, individual choice, was considered indecent, the two discussed political problems and theories, leading to a romantic relationship.

In Paris, Cai organized the Work and Study Cooperative Society (Gongxue huzhu she) and advocated Marxist communism.

[6] After the Chinese Communist Party was founded, Cai wrote and gained permission to establish an official branch in Europe.

In the latter half of 1921, Cai was arrested by the French government for organizing a wave of protests against the Work-Study leadership over admissions to the Sino-French Institute at the University of Lyons, and was deported soon after.

He was arrested in British Hong Kong and extradited to the Chinese authorities in Guangzhou, which was controlled by the warlord Chen Jitang.

[1] The ex-wife of Cai, Xiang Jingyu, was arrested a few years earlier in the Shanghai French Concession in Wuhan on 20 March 1928 due to the betrayal of members of her group to the police.