2004 United States presidential election in Pennsylvania

The 2004 United States presidential election in Pennsylvania took place on November 2, 2004, and was part of the 2004 United States presidential election. Voters chose 21 representatives, or electors to the Electoral College, who voted for president and vice president.

Pennsylvania was won by Democratic nominee John Kerry by a 2.50% margin of victory. Prior to the election, most news organizations considered this a toss-up, or swing state. Although the Commonwealth of Pennsylvania voted for the Democratic presidential nominee in six subsequent elections since 1992, the margins of victory had become smaller over the past elections. On election day, Kerry won the state with 50.92% of the vote, but won only 13 of the 67 counties in Pennsylvania. Most of these 13 counties have the highest populations in the commonwealth. The biggest key to Kerry's victory was winning Philadelphia County with 80.44% of the vote.

Bush was the first president elected to two terms without carrying Pennsylvania either time since Woodrow Wilson in 1912 and 1916, and is the only Republican president to not win the state at least once. This to date is the most recent election where Pennsylvania would back the losing candidate, and is thus tied with Wisconsin and Michigan as having the longest bellwether streak in the nation. This was also the first time since 1968 that Pennsylvania voted against the winner of the national popular vote.

As of 2022, this is the last time that Pennsylvania voted to the left of New Mexico and Nevada.