A by-election for the Tokyo 10th district in the Japanese Japanese House of Representatives was held on 23 October 2016 to replace Yuriko Koike, who vacated the seat to contest the Tokyo gubernatorial election in July 2016. Koike, a member of the Liberal Democratic Party (LDP), had represented the district since the December 2012 general election and also served a previous term from 2005 to 2009. The election was won by LDP candidate Masaru Wakasa, an incumbent member for the Tokyo proportional representation block who had supported Koike during her gubernatorial campaign. A separate by-election for the Fukuoka 6th district was held on the same day.