Ronald Harold Johnson is an American politician serving as the senior United States senator from Wisconsin, a seat he has held since 2011. A Republican, Johnson was first elected to the U.S. Senate in 2010, defeating Democratic incumbent Russ Feingold. He was reelected in 2016, defeating Feingold in a rematch, and in 2022, narrowly defeating Lieutenant Governor Mandela Barnes.

The 2010 United States Senate election in Wisconsin was held on November 2, 2010. Incumbent Democratic Senator Russ Feingold lost re-election to a fourth term to Republican challenger Ron Johnson, a businessman and first-time candidate. Johnson was the first Republican to win a Senate election in Wisconsin since 1986. Feingold also became the fifth senator in a row from Wisconsin's Class 3 Senate seat to be defeated for re-election in the general election, and the seventh in a row overall to lose by a defeat in either the primary or general elections. Johnson was re-elected in 2016 in a rematch with Feingold.