The roots of the State Bank of India lie in the first decade of the 19th century, when the Bank of Calcutta, later renamed the Bank of Bengal, was established on 2 June 1806. The Bank of Bengal was one of three Presidency banks, the other two being the Bank of Bombay (incorporated on 15 April 1840) and the Bank of Madras (incorporated on 1 July 1843). All three Presidency banks were incorporated as joint stock companies and were the result of royal charters. These three banks received the exclusive right to issue paper currency till 1861 when, with the Paper Currency Act, the right was taken over by the Government of India. The Presidency banks amalgamated on 27 January 1921, and the re-organised banking entity took as its name Imperial Bank of India. The Imperial Bank of India remained a joint stock company but without Government participation.
Pursuant to the provisions of the State Bank of India Act of 1955, the Reserve Bank of India, which is India's central bank, acquired a controlling interest in the Imperial Bank of India. On 1 July 1955, the imperial Bank of India became the State Bank of India. In 2008, the Government of India acquired the Reserve Bank of India's stake in SBI so as to remove any conflict of interest because the RBI is the country's banking regulatory authority.
Today, State Bank of India (SBI) is an Indian multinational, public sector banking and financial services company. It is a government-owned corporation with its headquarters in Mumbai, Maharashtra. On 1st April, 2017, State Bank of India, which is India's largest Bank merged with five of its Associate Banks (State Bank of Bikaner & Jaipur, State Bank of Hyderabad, State Bank of Mysore, State Bank of Patiala and State Bank of Travancore) and Bharatiya Mahila Bank with itself. This is the first ever large scale consolidation in the Indian Banking Industry. With the merger, State Bank of India will enter the league of top 50 global banks with a balance sheet size of ₹33 trillion, 278,000 employees, 420 million customers, and more than 24,000 branches and 59,000 ATMs. SBI's market share will increase to 22 percent from 17 per cent. It has 198 offices in 37 countries; 301 correspondents in 72 countries. The company is ranked 232nd on the Fortune Global 500 list of the world's biggest corporations as of 2016.
Apart from its five associate banks, SBI also has the following non-banking subsidiaries:

• SBI Capital Markets Ltd
• SBI Funds Management Pvt Ltd
• SBI Factors & Commercial Services Pvt Ltd
• SBI Cards & Payments Services Pvt. Ltd. (SBICPSL)
• SBI DFHI Ltd
• SBI Life Insurance Company Limited
• SBI General Insurance