The Philadelphia Inquirer is a daily newspaper headquartered in Philadelphia, Pennsylvania. The newspaper's circulation is the largest in both the U.S. state of Pennsylvania and the Delaware Valley metropolitan region of Southeastern Pennsylvania, South Jersey, Delaware, and the northern Eastern Shore of Maryland, and the 17th largest in the United States as of 2017.

Founded on June 1, 1829 as The Pennsylvania Inquirer, The Philadelphia Inquirer is the third-longest continuously operating daily newspaper in the nation. It has won 20 Pulitzer Prizes as of 2020.

The Inquirer first became a major newspaper during the American Civil War. The paper's circulation dropped after the Civil War's conclusion but then rose again by the end of the 19th century. Originally supportive of the Democratic Party, The Inquirer's political orientation eventually shifted toward the Whig Party and then the Republican Party before officially becoming politically independent in the middle of the 20th century. By the end of the 1960s, The Inquirer trailed its chief competitor, The Philadelphia Evening Bulletin, and lacked modern facilities and experienced staff. In the 1970s, however, new owners and editors turned the newspaper into one of the country's most prominent.

The newspaper is owned by The Philadelphia Inquirer, LLC, which also publishes Philadelphia Daily News, the city's daily tabloid, and a news portal (philly.com). The newspaper's publisher and chief executive officer is Elizabeth H. Hughes, and its editor is Gabriel Escobar.