British Hong Kong was a colony and dependent territory of the British Empire from 1841 to 1997, apart from a brief period under Japanese occupation from 1941 to 1945. The colonial period began with the occupation of Hong Kong Island in 1841 during the First Opium War. The island was ceded by Qing Empire in the aftermath of the war in 1842 and established as a Crown colony in 1843. The colony expanded to the Kowloon Peninsula in 1860 after the Second Opium War and was further extended when the UK obtained a 99-year lease of the New Territories in 1898.
Although Hong Kong Island and Kowloon were ceded in perpetuity, the leased area comprised vast majority of the overall territory and Britain considered that there was no viable way to divide the now single colony, while the Chinese Communist Party would not consider extending the lease or allowing British administration thereafter. The UK eventually agreed to transfer the entire colony to China upon the expiration of that lease in 1997 after obtaining guarantees to preserve its systems, freedoms, and way of life for at least 50 years.