Nie Yuanzi (5 April 1921 – 28 August 2019) was a Chinese academic administrator at Peking University, known for writing a big-character poster criticising the university for being controlled by the bourgeoisie, which is considered to have been the opening shot of the Cultural Revolution. She became a top leader of the Red Guards in Beijing, and was sentenced to 17 years in prison after the end of the Cultural Revolution.

Nie was born in 1921 into a wealthy family in Hua County, Henan, the youngest of four siblings. Her eldest brother, Nie Zhen (聂真), was a founder of the Chinese Communist Party (CCP) cell in the county. He was married to Wang Qian, a senior CCP member and the ex-wife of then President Liu Shaoqi.

When the Second Sino-Japanese War broke out in July 1937, Nie, then sixteen years old, joined the Communist resistance in Shanxi, which was supported by warlord Yan Xishan. She received military training at the National Teachers' College in Taiyuan and joined the CCP in 1938. In the 1940s, Nie moved to the Communist base in Yan'an, where she met Kang Sheng and his wife Cao Yi'ou [zh].

After the surrender of Japan, Nie was sent to the formerly Japanese-occupied Northeast China in 1946, where she worked in the government of Qiqihar. A year later, she was appointed Director of the Theory Section of the Propaganda Department of Harbin. In 1959, she divorced her first husband Wu Hongyi (吴宏毅), with whom she had two children, after he was denounced as a "rightist" during the Anti-Rightist Campaign.

In 1963, Nie was transferred to Peking University, a turning point of her life. She served as Vice Chair of the Department of Economics and was appointed CCP Committee Secretary of the Department of Philosophy a year later. In early 1966, she married Wu Gaizhi [zh], an official in the powerful Central Commission for Discipline Inspection and a peer of the radical leader Kang Sheng. Many thought that she married him to further her own career.

On 25 May 1966, Nie put up a big-character poster on the campus of Peking University. The poster criticised Song Shuo, deputy director of the Beijing Municipal University Bureau, Lu Ping, the President of Peking University and head of its CCP committee, and Peng Peiyun, an official in the Beijing Municipal University Bureau. Although Nie's main criticism was over the control of Peking University by the bourgeoisie, the aim of the campaign was to legitimise the purge of the Beijing municipal party chief Peng Zhen, by exposing his alleged crime of supporting a bourgeoise reactionary education line. This was pushed by members of the radical left-lean clique surrounding Mao Zedong, including Kang Sheng and his wife Cao Yi'ou.The text of the big character poster was as follows:

"To hold meetings and to post big-character posters are mass militant methods of the best kind. But you 'lead' the masses by preventing them from holding meetings and putting up posters. You have manufactured various taboos and regulations. By so doing, have you not suppressed, forbidden, and opposed the mass revolution? We absolutely will not allow you to do so!

You shout about 'strengthening the leadership and standing fast at one's post.' You still want to 'stand fast' at your 'posts' in order to sabotage the Cultural Revolution. We warn you that a mantis cannot stop the wheels of a cart, and mayflies cannot topple a giant tree. You are daydreaming!