| Election Name: | 2002 United States Senate election in South Dakota |
| Country: | South Dakota |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1996 United States Senate election in South Dakota |
| Previous Year: | 1996 |
| Next Election: | 2008 United States Senate election in South Dakota |
| Next Year: | 2008 |
| Election Date: | November 5, 2002 |
| Image1: | Tim Johnson official portrait, 2009.jpg |
| Nominee1: | Tim Johnson |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 167,481 |
| Percentage1: | 49.62% |
| Nominee2: | John Thune |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 166,957 |
| Percentage2: | 49.47% |
| Map Size: | 260px |
| U.S. Senator | |
| Before Election: | Tim Johnson |
| Before Party: | Democratic Party (United States) |
| After Election: | Tim Johnson |
| After Party: | Democratic Party (United States) |
The 2002 United States Senate election in South Dakota was held on November 5, 2002. Incumbent Democratic U.S. Senator Tim Johnson narrowly won re-election to a second term over Republican John Thune by a margin of 524 votes, or 0.15%. This made the election the closest race of the 2002 Senate election cycle.
Thune later narrowly won South Dakota's other U.S. Senate seat in 2004, and was re-elected in 2010, 2016, and 2022 in uncompetitive elections.
Thune ran against Tim Johnson, who narrowly won his first senate election in 1996. Thune launched a television advertising campaign mentioning al Qaeda and Saddam Hussein, contending that both are seeking nuclear weapons and that this country needs a missile defense system, something Johnson voted against 29 times and that Thune supports. The incumbent attacked Thune for politicizing national security.[1] President George W. Bush campaigned for Thune in late October.[2] More than $20 million was spent in the election. Both candidates had raised over $5 million each.[3]
Johnson narrowly prevailed over Thune by a mere 524 votes. Despite the extremely close results, Thune did not contest the results and conceded defeat on the late afternoon of November 9. Johnson's narrow victory may be attributed to his strong support in Oglala Lakota County, and to Thune also underperforming in typically Republican areas. Johnson was sworn in for a second term on January 3, 2003. Thune was elected to South Dakota's other Senate seat in 2004, defeating incumbent minority leader Tom Daschle. He served alongside Johnson until the latter retired in 2015.