The typical history of Hong Kong begins around 1840. The previous year had seen the outbreak of what has since become known as the first Opium War between China's Qing dynasty (1644–1911) and Britain. Although prompted by the highly-exploitative opium trade, the conflict was also about wider issues of diplomatic status and representation and the management of trade. British gunboats prevailed against a weak Qing counterpart, and during the conflict British forces occupied the small island of Hong Kong at the mouth of the Pearl River which led inland to the southern city of Canton (today known as Guangzhou), planting their flag in Hong Kong in January 1841. The Treaty of Nanking which ended the first Opium War in 1842 – the first of the so-called “unequal treaties” – included provision for the Qing to cede Hong Kong to the British in perpetuity.

This initial imperial outpost was expanded in 1860 after the second Opium War by the ceding of the Kowloon peninsula, only 20 square kilometres of land which sat across the deep natural harbour from Hong Kong island. At the end of the nineteenth century, a wider scramble among western powers for concessions from the Qing saw Britain expand its colony further, with the addition of land to the north of the Kowloon peninsula and some 230 outlying islands. At over 930 square kilometres these New Territories constitute the vast majority of the 1,100 square kilometres of Hong Kong as a whole (Hong Kong's boundaries today also encompass 1,650 square kilometres of sea). Under the terms of the Convention of Peking of 1898, the New Territories were not ceded, but leased to Britain for a period of 99 years, and only occupied after brief resistance from the indigenous inhabitants of the area was overcome. With a Royal Order in Council stipulating British rule until 30 June 1997, the future “appointment with China” was set.

In contemporary China, the year 1840 has taken on a significance beyond its direct relevance to Hong Kong. This is the year when, in the writing of Chinese history, “modern” Chinese history begins. It is a much-cited date in official Chinese speeches and publications, and its significance for Chinese nationalists (including in the Communist Party) has been as a marker of the start of the “century of humiliation”, China's subjugation to western powers.