The 2018 United States Senate election in Indiana took place on November 6, 2018, along with other elections to the United States Senate and House of Representatives and various state and local elections. Incumbent Democratic Senator Joe Donnelly lost re-election to a second term to Republican Mike Braun by a 6% margin. This was the second consecutive election for this seat where the incumbent was defeated and/or the seat flipped parties.

The 2018 United States Senate elections were held on November 6, 2018. Among the 100 seats, the 33 of Class 1 were contested in regular elections while 2 others were contested in special elections due to Senate vacancies in Minnesota and Mississippi. The regular election winners were elected to 6-year terms running from January 3, 2019, to January 3, 2025. Senate Democrats had 26 seats up for election, while Senate Republicans had 9 seats up for election.