The 2010 Wisconsin Senate elections were held on Tuesday, November 2, 2010. Seventeen of the 33 seats in the Wisconsin State Senate were up for election—the odd-numbered districts. Before the election, 18 Senate seats were held by Democrats and 15 seats were held by Republicans. 10 Democratic seats and 7 Republican seats were up in this election. The primary election took place on September 14, 2010.
Republicans flipped four Democratic-held Senate seats and achieved a majority for the first time since 2004, entering the 100th Wisconsin Legislature with 19 of 33 State Senate seats.
Seats where the margin of victory was under 10%: