Union Bank of India (UBI) was registered on 11 November 1919 as a limited company in Mumbai and was inaugurated by Mahatma Gandhi. At the time of India's Independence in 1947, UBI only had four branches – three in Mumbai and one in Saurashtra, all concentrated in key trade centres. After Independence UBI accelerated its growth and by the time the government nationalized it in 1969, it had grown to 240 branches in 28 states. Shortly after nationalization, UBI merged in Belgaum Bank, a private sector bank established in 1930 that had itself merged in a bank in 1964, the Shri Jadeya Shankarling Bank. Then in 1985 UBI merged in Miraj State Bank, which had been established in 1929. In 1999 the Reserve Bank of India requested that UBI acquire Sikkim Bank in a rescue after extensive irregularities had been discovered at the non–scheduled bank. Sikkim Bank had eight branches located in the North–east, which was attractive to UBI.

UBI began its international expansion in 2007 with the opening of representative offices in Abu Dhabi, United Arab Emirates, and Shanghai, Peoples Republic of China. The next year, UBI established a branch in Hong Kong, its first branch outside India. In 2009, UBI opened a representative office in Sydney, Australia.

Union Bank has been playing a very proactive role in the economic growth of India and it extends credit for the requirements of different sectors of economy. Industries, exports, trading, agriculture, infrastructure and the individual segments are sectors in which the bank has deployed credit to spur economic growth and to earn from a well diversified portfolio of assets.

At the end of March 2015 the Bank achieved total business level of Rs. 5,79,627 crore (Rupees five lakh seventy Nine thousand six hundred and twenty seven crore).