Chen Duxiu (simplified Chinese: 陈独秀; traditional Chinese: 陳獨秀; pinyin: Chén Dúxiù; Wade–Giles: Chʻên Tu-hsiu; 9 October 1879 – 27 May 1942) was a Chinese intellectual, revolutionary, and political activist who co-founded the Chinese Communist Party (CCP) with Li Dazhao in 1921 and served as its first General Secretary from 1921 to 1927. Chen was also a leading figure in the New Culture Movement (c. 1915–1922) and May Fourth Movement of 1919, which significantly influenced China's intellectual and political landscape in the early 20th century.

Born in Anhui, Chen was raised in a traditional gentry family but became involved in revolutionary activities from a young age. He studied in Japan, where he was exposed to Western ideas and became involved with Chinese student activist groups. Returning to China, he played a key role in local revolutionary movements in Anhui, notably through journalism and education, advocating for a vernacular literary revolution and the preservation of China's "national essence". During the New Culture Movement, Chen rose to national prominence as the editor of the influential magazine New Youth (Xin Qingnian) and as Dean of Arts and Letters at Peking University. He championed science, democracy, and vernacular literature, while launching trenchant critiques of traditional Confucianism and Chinese society. His writings and leadership were instrumental in shaping the May Fourth generation of intellectuals and activists.

Following the May Fourth Movement and influenced by the Russian Revolution, Chen embraced Marxism and, with the assistance of Comintern agents, co-founded the CCP. As its first leader, he navigated the complex early years of the party, including the First United Front with the Kuomintang (KMT). However, he was removed from leadership in 1927, becoming a scapegoat for the failures of the United Front. Subsequently, Chen became associated with the Trotskyist Left Opposition and was expelled from the CCP in 1929. He spent his later years in relative political isolation, attempting to reconcile Marxism with his earlier democratic ideals and continuing his philological research until his death in Sichuan in 1942.

Chen Duxiu's legacy is complex. While often criticized in official CCP historiography for "right-wing opportunism", he is recognized as a founder of the party and a pivotal figure in modern Chinese intellectual and revolutionary history. He represented the internationalistic and Westernizing Marxist influences of the early CCP, which were later superseded by the more nationalist and voluntaristic tendencies of Mao Zedong.

Chen Duxiu was born on 9 October 1879 in Anqing, Anhui. He provided scant details about his early life in his unfinished autobiography, recalling himself as a "fatherless child". His father, a minor official and tutor, died when Chen was two years old, not two months as Chen later claimed. After his father's death, Chen was adopted by his paternal uncle, Chen Xifan, a powerful official who amassed considerable wealth, partly through business dealings involving a British firm and soybean exports from Manchuria where he served. This uncle's beneficent influence contrasted with the harshness of Chen's grandfather, whom Chen described as an opium-smoking, tyrannical figure who oversaw his early education. Chen's portrayal of his grandfather may have been crafted to appeal to the anti-patriarchal sentiments of the youth he later led.

The Chen family was an "up-and-coming" one that had improved its social standing through hard work and enterprise rather than solely through official connections. Chen Xifan, despite his relative wealth and official position, was described as an unpretentious man with a common touch. The family's pragmatic approach and engagement with Western commercial opportunities likely influenced Chen's later views on national development and his critique of traditional elites who he felt hindered China's progress.

Chen was immersed in Confucian classics from a young age. He reportedly found the official eight-legged essay style tedious, preferring the 6th-century poetry anthology Zhaoming Wenxuan, which contained many obscure characters. This interest in obscure characters hinted at an early inclination towards the kaozheng (evidential research) school of scholarship, known for its critical approach to neo-Confucian orthodoxy. He also read the works of the 18th-century poet Yuan Mei, an advocate for women's rights and a critic of the examination system.

In 1896, at the age of 17, Chen passed the imperial xiucai examination, ranking first in his district. The following year, he travelled to Nanjing to sit for the higher-level juren examination, an experience he vividly described in his autobiography. He was disappointed by the city's condition and the crude behavior of fellow students, but the gathering of young scholars also provided an opportunity for the exchange of new ideas. It was during this period, following China's defeat by Japan in 1895, that reformist ideas, particularly those of Kang Youwei and Liang Qichao disseminated through publications like Shiwu Bao (Chinese Progress), began to circulate widely. Chen was attracted to these new iconoclastic views, finding in them a path to respectable engagement with Western learning, which he had previously seen as subservient to foreign powers.