Masovian Voivodeship Sejmik
The Masovian Voivodeship Sejmik is the regional legislature of the Voivodeship of Masovia in Poland. It is a unicameral parliamentary body consisting of fifty-one councillors, making it the largest provincial assembly in the republic. All councillors are chosen during regional elections for a five-year term. Incumbent chairperson of the assembly is Ludwik Rakowski of the Civic Coalition, elected at the first session on 7 May 2024.
The assembly elects the executive board that acts as the collective executive for the provincial government, headed by the voivodeship marshal. The current executive board of Masovia is a coalition government between the Civic Coalition and Polish People's Party under the leadership of Marshal Adam Struzik of the PSL.
The assembly convenes at the Palace of the Treasury Minister in Warsaw.
Constituencies
Members of the assembly are elected in seven multi-member constituencies with the party-list proportional representation using D'Hondt apportionment method.| Constituency number | City counties | Land counties | Seats |
| 1 | Part of Warsaw | 5 | |
| 2 | Part of Warsaw | 5 | |
| 3 | Part of Warsaw | 6 | |
| 4 | Płock | Ciechanów, Gostynin, Mława, Płock, Płońsk, Przasnysz, Pułtusk, Sierpc, Sochaczew, Żuromin, Żyrardów | 8 |
| 5 | Radom | Białobrzegi, Grójec, Kozienice, Lipsko, Przysucha, Radom, szydłowiecki, zwoleński | 7 |
| 6 | Ostrołęka, Siedlce | Garwolin, Łosice, Maków, Mińsk, Ostrołęka, Ostrów, Siedlce, Sokołów, Węgrów, Wyszków | 9 |
| 7 | Grodzisk, Legionowo, Nowy Dwór, Otwock, Piaseczno, Pruszków, Warsaw West, Wołomin | 11 |