The 2008 United States Senate election in Iowa was held on November 4, 2008. Incumbent Senator Tom Harkin sought re-election to a fifth term in office. Unlike Harkin's three previous reelection bids, he was not challenged by a sitting United States Congressman but instead faced small businessman Christopher Reed, who won the Republican primary by just a few hundred votes. Harkin defeated Reed in a landslide, winning 94 of Iowa's 99 counties. As of 2023, this is the last time that a Democrat has won a U.S. Senate election in Iowa.

Thomas Richard Harkin is an American lawyer, author, and politician who served as a United States senator from Iowa from 1985 to 2015. A member of the Democratic Party, he previously was the U.S. representative for Iowa's 5th congressional district from 1975 to 1985. He is the longest-serving senator to spend the entire tenure as a state's junior senator.