The Four Olds (simplified Chinese: 四旧; traditional Chinese: 四舊; pinyin: sì jiù) refer to categories used by the Red Guards during the Cultural Revolution to characterize elements of Chinese culture prior to the Chinese Communist Revolution that they were attempting to destroy. The Four Olds were 'old ideas', 'old culture', 'old customs', and 'old habits'. During the Red August of 1966, shortly after the onset of the Cultural Revolution, the Red Guards' campaign to destroy the Four Olds began amid the massacres being carried out in Beijing.

The term "Four Olds" first appeared on 1 June 1966, in Chen Boda's People's Daily editorial, "Sweep Away All Cow Demons and Snake Spirits", where the Old Things were described as anti-proletarian, "fostered by the exploiting classes, [and to] have poisoned the minds of the people for thousands of years". However, which customs, cultures, habits, and ideas specifically constituted the "Four Olds" were never clearly defined.

On 8 August, the Central Committee of the Chinese Communist Party used the term at its 8th National Congress. The term was endorsed on 18 August by Lin Biao at a mass rally, and from there it spread to Red Flag magazine, as well as to Red Guard publications. During this time, changes associated with the destruction of the Four Olds included: renaming places and people with "revolutionary names", destruction of historical and religious sites and texts, and the arrest of clergy.

Calls to destroy the "Four Olds" usually did not appear in isolation, but were contrasted with the hope of building the "Four News" (new customs, new culture, new habits, new ideas). Newborn socialist things were said to struggle against the Four Olds. The idea that Chinese culture was responsible for China's economic backwardness and needed to be reformed had some precedent in the May Fourth Movement (1919), and was also encouraged by colonial authorities during the Second Sino-Japanese War.

The campaign to Destroy the Four Olds and Cultivate the Four News (Chinese: 破四旧立四新; pinyin: Pò Sìjiù Lì Sìxīn) began in Beijing on 19 August during the "Red August". Academic Alessandro Russo writes that the destruction of the Four Olds was an ambiguous campaign from the perspective of the Chinese Communist Party. He argues that in a time of increasing political pluralization, the Party sought to channel student activism towards obvious class enemies and less relevant objectives to make it easier for the Party to contain the situation.

Across China, signs bearing old road names were vandalized and renamed. The first things to change were the names of streets and stores: "Blue Sky Clothes Store" to "Defending Mao Zedong Clothes Store", "Cai E Road" to "Red Guards Road", and so forth.

In Beijing, the name of the road where the embassy of the Soviet Union was stationed was changed to "Anti-revisionism Road". The Peking Union Medical College Hospital, founded in 1921 by the Rockefeller Foundation, was renamed "Anti-Imperialist Hospital".

In Huangpu district of Shanghai, the city's commercial center, Red Guards tore down 93 percent of shop signboards (2,166 of 2,328), and renamed restaurants, schools and hospitals. Red Guards also took Nanjing Road as their revolutionary headquarters in Shanghai, renaming it the "Anti-Imperialism Street".