The Zanzibar Revolution (Swahili: Mapinduzi ya Zanzibar; Arabic: ثورة زنجبار, romanized: Thawrat Zanjibār) began on 12 January 1964 and led to the overthrow of the Sultan of Zanzibar Jamshid bin Abdullah and his mainly Arab government by the island's majority Black African population.

Zanzibar was an ethnically diverse state consisting of a number of islands off the east coast of Tanganyika. Formally separated from German East Africa in 1890, it had become fully independent in 1963, with responsibility for its own defense and foreign affairs, as a result of Britain giving up its protectorate over it. In a series of parliamentary elections preceding this change, the Arab minority succeeded in retaining the hold on power it had inherited from Zanzibar's former history as an overseas territory of Oman.

Frustrated by the lack of parliamentary representation compared to its share of votes in the July 1963 election, the African Afro-Shirazi Party (ASP), led by John Okello, mobilised around 600–800 men on the main island of Unguja on the morning of 12 January 1964. Having overrun the country's police force and appropriated their weaponry, the insurgents proceeded to Zanzibar Town, where they overthrew the Sultan and his government.

They conducted a massacre of Arabs during the Zanzibar Revolution. The insurgents also proceeded to loot Arab and South Asian–owned properties and businesses, and rape or murder Arab and Indian civilians on the island. The death toll is disputed, with estimates ranging from several hundreds to 20,000. An estimated 10,000 people escaped from the island, with many fleeing to the UK. Around a quarter of Zanzibar's Arabs were killed in the massacres. The moderate ASP leader Abeid Karume became the country's new president and head of state.

The new government's apparent communist ties concerned Western governments. As Zanzibar lay within the British sphere of influence, the British government drew up a number of intervention plans. However, the feared communist government never materialised. Because British and American citizens were successfully evacuated, the UK did not intervene in the island's unrest. The Eastern Bloc powers of East Germany and the Soviet Union, along with the anti-Soviet People's Republic of China, immediately recognised the new government and sent advisors.

Karume succeeded in negotiating a merger of Zanzibar with Tanganyika to form the new nation of Tanzania. Contemporary media assessed this merger as an attempt to prevent communist subversion of Zanzibar. The revolution ended more than 250 years of Arab dominance in Zanzibar. It is commemorated on the island each year with anniversary celebrations and a public holiday. The toll of victims in the massacres is generally not recognized.

The Zanzibar Archipelago, now part of the Southeast African republic of Tanzania, is a group of islands lying in the Indian Ocean off the coast of Tanganyika. It comprises the main southern island of Unguja (also known as Zanzibar), the smaller northern island of Pemba, and numerous surrounding islets. Merchants and traders regularly visited the islands from Persia, Arabia, and India, beginning around the millennium. Some settled there, and Islam became influential in island culture among all ethnicities.

The long history of Arab rule dated to 1698, and Zanzibar was an overseas territory of Oman until it achieved independence in 1858 under its own Sultanate. In 1890 during Ali ibn Sa'id's reign, Zanzibar became a British protectorate after the Heligoland–Zanzibar Treaty separated British and German territory in Central Africa during the Scramble for Africa. Although never under direct British rule, it was considered part of the British Empire.