A voivodeship sejmik (Polish: sejmik wojewódzki) is a provincial-level elected assembly for each of the 16 voivodeships of Poland. Sejmiks are elected to four-year terms, decided during nationwide local elections. The size of the legislative assembly varies for each voivodeship depending on the population; in lower populated voivodeships, there are 30 representatives, while in the most populous (Masovian Voivodeship) there are 51 members. The current assemblies were created during the local government reforms passed by the Sejm in 1998.

The word sejmik is a diminutive of sejm, a historical term for an assembly of nobles, and is now the name of the lower house of the Polish National Assembly. The word sejmik was consciously chosen by lawmakers in order to eliminate the term rada wojewódzka (voivodeship council), as the definition conjured memories of voivodeship people's councils during the communist People's Republic of Poland era.

The members of a sejmik elect a chairman and deputy chairmen from among their ranks. These may not sit on the voivodeship's governing zarząd województwa (executive board). The chairman is responsible for organizing the sejmik's business and presiding over debates.