The 2015 Louisiana State Senate election was held on October 24, 2015, with runoff elections taking place on November 21, 2015, to determine which party would control the Louisiana State Senate for the following four years in the 71st Louisiana Legislature. All 39 seats in the Louisiana State Senate were up for election and the primary was held on October 24, 2015. The elections for state senate were held alongside concurrent State House elections. Under the Louisiana primary system, all candidates appeared on the same ballot, regardless of party. Four districts held runoff elections on November 21, 2015, due to no candidate receiving a majority of the vote in the general election. Prior to the election, 26 seats were held by Republicans and 13 seats were held by Democrats. The general election saw Democrats gain a single seat, meaning that the Republicans retained their majority in the State Senate.
Seats where the margin of victory was under 10%: