The Dominion of India, officially the Union of India, was an independent dominion in the British Commonwealth of Nations existing between 15 August 1947 and 26 January 1950. Until its independence, India had been ruled as an informal empire by the United Kingdom. The empire, also called the British Raj and sometimes the British Indian Empire, consisted of regions, collectively called British India, that were directly administered by the British government, and regions, called the princely states, that were ruled by Indian rulers under a system of paramountcy, in favour of the British. The Dominion of India was formalised by the passage of the Indian Independence Act 1947, which also formalised an independent Dominion of Pakistan—comprising the regions of British India that are today Pakistan and Bangladesh. The Dominion of India remained "India" in common parlance but was geographically reduced by the lands that went to Pakistan, as a separate dominion. Under the Act, the King remained the monarch of India but the British government relinquished all responsibility for administering its former territories. The government also revoked its treaty rights with the rulers of the princely states and advised them to join in a political union with India or Pakistan. Accordingly, one of the British monarch's regnal titles, "Emperor of India," was abandoned.
The Dominion of India came into existence on the partition of India and was beset by religious violence. Its creation had been preceded by a pioneering and influential anti-colonial nationalist movement which became a major factor in ending the British Raj. A new government was formed led by Jawaharlal Nehru as prime minister, and Vallabhbhai Patel as deputy prime minister, both members of the Indian National Congress. Lord Mountbatten, the last Viceroy, stayed on until June 1948 as independent India's first governor-general; he was replaced by C. Rajagopalachari.