United Overseas Bank Limited (Chinese: 大華銀行有限公司; pinyin: Dàhuá Yínháng Yǒuxìan Gōngsī; Pe̍h-ōe-jī: Tāi-hôa Gûn-hâng Iú-hān Kong-si), often known as UOB, is a Singaporean regional bank headquartered at Raffles Place, Singapore, with branches mostly found in Southeast Asia countries.

It is one of the three "big local banks" in the country, the other two being DBS Bank and Oversea-Chinese Banking Corporation (OCBC).

First Founded during the Great Depression in 1935 as United Chinese Bank (UCB) by a group of Hoklo businessmen including Sarawak-born Wee Kheng Chiang, the bank operated from a single branch bank in rented premises of Bonham Building, located in Boat Quay, close to the Singapore River. It was principally engaged in short-term loans to a segment of local businessmen, to be precise, Hokkien Chinese businessmen in Singapore.

UOB is the third largest bank in Southeast Asia by total assets. The bank provides personal financial services, commercial banking, private banking and asset management services, as well as corporate finance, venture capital and insurance services. It has 68 branches in Singapore and a network of more than 500 offices in 19 countries and territories in Asia Pacific, Western Europe and North America.

On 6 August 1935, Sarawak-born businessman Wee Kheng Chiang, together with six other partners, established the bank with a paid-up capital of S$1 million. The bank was originally incorporated as United Chinese Bank (UCB) and served the mainly Hokkien Chinese community in Singapore. Wee, being the largest shareholder, became its first chairman. In October 1935, UCB opened for business in the three-story Bonham Building. On 23 January 1965, UCB changed its name to United Overseas Bank (Chinese name unchanged) to avoid duplication with another United Chinese Bank in Hong Kong (simplified Chinese: 中国联合银行; traditional Chinese: 中國聯合銀行), and opened its first overseas branch in Hong Kong.

In 1970, UOB was listed on the Joint Stock Exchange of Singapore and Malaysia. At the time, the stock exchange had an office in both Singapore and Kuala Lumpur. After it was publicly listed, the bank went through a series of targeted acquisitions. The bank first acquired the controlling stake of Chung Khiaw Bank in 1971, which expanded its domestic presence and also gave the bank offices in Malaysia and Hong Kong. A new logo for both United Overseas Bank and Chung Khiaw Bank was launched in January 1972.

In 1973, UOB acquired Lee Wah Bank, which was originally founded in 1920 by Eu Tong Sen with Cheong Yoke Choy as one of its co-founders and original directors, provided services in Malaysia and Singapore. In that same year, the bank built a new 30-storey office tower in place of the Bonham Building, which was named the UOB Building (now known as UOB Plaza Two). The company continued with acquisitions, with Far Eastern Bank in 1984, Westmont Bank (now known as UOB Philippines) and Radanasin Bank (now known as United Overseas Bank (Thai) Public Company Limited) in 1999.

In September 2001, UOB acquired Overseas Union Bank, then Singapore's fourth largest local bank, in a deal worth S$10 billion.