Handover of Macau in the context of "Proclamation of the People's Republic of China"

The Portuguese Empire was a colonial empire that existed between 1415 and 1999. In conjunction with the Spanish Empire, it ushered in the European Age of Discovery. It achieved a global scale, controlling vast portions of the Americas, Africa and various islands in Asia and Oceania. It was one of the most powerful empires of the early modern period, while at its greatest extent in 1820, covering 5.5 million square km (2.1 million square miles), making it among the largest empires in history. Composed of colonies, factories, and later overseas territories, it was the longest-lived colonial empire in history, from the conquest of Ceuta in North Africa in 1415 to the handover of Macau to China in 1999.

The power and influence of the Kingdom of Portugal would eventually expand across the globe. In the wake of the Reconquista, Portuguese sailors began exploring the coast of Africa and the Atlantic archipelagos in 1418–1419, using recent developments in navigation, cartography, and maritime technology such as the caravel, with the aim of finding a sea route to the source of the lucrative spice trade. In 1488, Bartolomeu Dias rounded the Cape of Good Hope and Cape Agulhas, and in 1498 Vasco da Gama reached India. In 1500, Pedro Álvares Cabral, while on a voyage to India, reached what would later be Brazil.

Decolonization is the undoing of colonialism, the latter being the process whereby imperial nations establish and dominate foreign territories, often overseas. The meanings and applications of the term are disputed. Some scholars of decolonization focus especially on independence movements in the colonies and the collapse of global colonial empires.

As a movement to establish independence for colonized territories from their respective metropoles, decolonization began in 1775 with the American Revolution in North America against the British Empire. The Napoleonic Wars in the 19th century saw the French colonial empire, the Spanish Empire, and Portugal face decolonization with the Haitian Revolution, the Spanish American wars of independence, and the independence of Brazil from Portugal. A major wave of decolonization occurred in the aftermath of the First World War, including in the United States and the Empire of Japan. Another wave of decolonization occurred after the Second World War, and many countries gained their independence in the following years. The last wave of decolonization occurred after the Cold War with the collapse of the Soviet Union, the independence of Palau, and the handovers of Hong Kong and Macau. Seventeen territories remain under the United Nations classification of non-self-governing territories.

The handover of Hong Kong from the United Kingdom of Great Britain and Northern Ireland to the People's Republic of China occurred at midnight on 1 July 1997. This event ended 156 years of British rule, dating back to the cession of Hong Kong Island in 1841 during the First Opium War.

Hong Kong was a colony of the British Empire from 1841, except during the Japanese occupation of Hong Kong from 1941 to 1945. Its territory expanded after the First Opium War with the addition of the Kowloon Peninsula and Stonecutters Island in 1860 and the New Territories in 1898 under a 99-year lease. The 1984 Sino–British Joint Declaration set the terms of the 1997 handover, under which China pledged to uphold "one country, two systems" for 50 years. Hong Kong became China's first special administrative region, followed by Macau in 1999 under similar arrangements. With a population of about 6.5 million in 1997, Hong Kong made up 97 percent of the population of all the British Dependent Territories and was Britain's last major colony.

Macau was under Portuguese rule from the establishment of the first official Portuguese settlement in 1557 until its handover to China in 1999. It comprised the Municipality of Macau and the Municipality of Ilhas. Macau was both the first and last European holding in China.

Macau's history under Portugal can be broadly divided into three distinct political periods. The first was the establishment of the Portuguese settlement in 1557 to 1849. The Portuguese had jurisdiction over the Portuguese community and certain aspects of the territory's administration but no real sovereignty. Next came the colonial period, which scholars generally place from 1849 to 1974. As Macau's importance among other territories grew within the Portuguese Empire, Portuguese sovereignty over Macau strengthened and it became a constitutional part of Portuguese territory. Chinese sovereignty during this era was mainly nominal. Finally, in the aftermath of the 12-3 incident in 1966, the third was the transition period or post-colonial period, after the Carnation Revolution in 1974 until the handover in 1999.