State Bank of India (SBI) is an Indian multinational public sector bank and financial services statutory body, headquartered in Mumbai. It is the largest bank in India with a 23% market share by assets and a 25% share of the total loan and deposits market. It is also the tenth largest employer in India with nearly 250,000 employees. As of 2024, SBI has 500 million customers.

The Reserve Bank of India (RBI) has identified SBI, HDFC Bank, and ICICI Bank as domestic systemically important banks (D-SIBs), which are often referred to as banks that are "too big to fail". SBI is the 43rd largest bank in the world by total assets and ranked 163rd in the Fortune Global 500 list of the world's biggest corporations of 2025. In 2024, SBI was ranked 55th in Forbes Global 2000.

The bank descends from the Bank of Calcutta, founded in 1806 via the Imperial Bank of India, making it the oldest commercial bank in the Indian subcontinent. The Bank of Madras merged into the other two presidency banks in British India, the Bank of Calcutta and the Bank of Bombay, to form the Imperial Bank of India, which in turn became the State Bank of India on 1 July 1955. Over the course of its 200-year history, the bank has been formed from the mergers and acquisitions of more than twenty banks. The Government of India took control of the Imperial Bank of India in 1955, with Reserve Bank of India (India's central bank) taking a 60% stake, renaming it State Bank of India.

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 (est. 15 April 1840) and the Bank of Madras (est. 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.

Under 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 to remove any conflict of interest because the RBI is the country's banking regulatory authority.

In 1959, the government passed the State Bank of India (Subsidiary Banks) Act. This made eight banks that had belonged to princely states into subsidiaries of SBI. This was during the First Five-Year Plan, which prioritised the development of rural India. The government integrated these banks into the State Bank of India system to expand its rural outreach. In 1963, SBI merged the State Bank of Jaipur (est. 1943) and State Bank of Bikaner (est.1944).

SBI has acquired local banks in rescues. The first was the Bank of Bihar (est. 1911), which SBI acquired in 1969, together with its 28 branches. The next year, SBI acquired the National Bank of Lahore (est. 1942), which had 24 branches. Five years later, in 1975, SBI acquired Krishnaram Baldeo Bank, which had been established in 1916 in Gwalior State, under the patronage of Maharaja Madho Rao Scindia. The bank had been the Dukan Pichadi, a small moneylender, owned by the Maharaja. In 1985, SBI acquired the Bank of Cochin in Kerala, which had 120 branches. SBI was the acquirer as its affiliate, the State Bank of Travancore, already had an extensive network in Kerala.

In March 2001, SBI partnered with BNP Paribas to form a 76:24 joint venture life insurance company named SBI Life Insurance Company.