The Kostroma Oblast Duma () is the regional parliament of Kostroma Oblast, a federal subject of Russia. A total of 35 deputies are elected for five-year terms.

Elections 2005

PartySeats United Russia 14 Communist Party of the Russian Federation 5 Agrarian Party of Russia 4 Rodina 2 Liberal Democratic Party of Russia 2 Russian Party of Life 1

2010 PartySeats United Russia 26 Communist Party of the Russian Federation 4 SRZP 3 Liberal Democratic Party of Russia 2

2015 PartySeats United Russia 27 Communist Party of the Russian Federation 3 SRZP 2 Liberal Democratic Party of Russia 1

2020 PartySeats United Russia 24 SRZP 2 Communist Party of the Russian Federation 2 Party of Social Protection 2 Liberal Democratic Party of Russia 1 Russian Party of Pensioners for Social Justice 1 Yabloko 1 New People 1 Independent 1

2025 PartySeats United Russia 26 SRZP 3 Liberal Democratic Party of Russia 2 Communist Party of the Russian Federation 2 New People 1 Russian Party of Pensioners for Social Justice 1

References