The Union Bank of Delaware was a bank that operated in Wilmington, Delaware, from 1839 until its acquisition by Wilmington Trust in 1943. It was chartered as a state bank on February 15, 1839, and was "soon recognized as one of the leading financial institutions in the state". On June 20, 1865, it was certified as a national bank and subsequently renamed the Union National Bank. In January 1887, it was reorganized as a National Bank. In 1943, the bank was acquired by Wilmington Trust.