Fifth Third Bancorp is a bank holding company headquartered in Cincinnati, Ohio. It is the parent company of Fifth Third Bank (5/3 Bank), which operates 1,100 branches and 2,400 automated teller machines, across 12 states: Ohio, Florida, Georgia, Illinois, Indiana, Kentucky, Michigan, North Carolina, South Carolina, Tennessee, Alabama, and West Virginia. It is on the list of largest banks in the United States and is ranked 321st on the Fortune 500. The name "Fifth Third" is derived from the names of the bank's two predecessor companies, Fifth National Bank and Third National Bank, which merged in 1908.

On June 17, 1858, the Bank of the Ohio Valley, founded by William W. Scarborough, opened in Cincinnati, Ohio. On June 23, 1863, the Third National Bank was organized. On April 29, 1871, Third National Bank acquired Bank of the Ohio Valley. In 1888, Queen City National Bank changed its name to Fifth National Bank.

On June 1, 1908, Third National Bank and Fifth National Bank merged to become the Fifth–Third National Bank of Cincinnati; the hyphen was later dropped. The merger took place when prohibitionist ideas were gaining popularity, and it is a legend that "Fifth Third" was better than "Third Fifth", which could have been construed as a reference to three fifths of alcohol. The name went through several changes—the most recent being Fifth Third Union Trust Company—until March 24, 1969, when it was changed to Fifth Third Bank.

In 1999, the bank acquired Emerald Financial for $204 million.

In November 2008, the United States Department of the Treasury invested $3.4 billion in the company as part of the Troubled Asset Relief Program and in February 2011, the company repurchased the investment from the Treasury.

In 2009, Fifth Third completed the corporate spin-off of Fifth Third Processing Solutions, which was acquired by Worldpay, Inc. in 2012.

In May 2018, Fifth Third acquired MB Financial in a $4.7 billion transaction.

In August 2020, the bank partnered with Trust & Will.