Kazimierz Marcinkiewicz, Polish physicist and politician, 12th Prime Minister of Poland

Kazimierz Marcinkiewicz is a Polish conservative politician who served as Prime Minister of Poland from 31 October 2005 to 14 July 2006. He was a member of the Law and Justice party.

The president of the Council of Ministers, colloquially and commonly referred to as the prime minister, is the head of the cabinet and the head of government of Poland. The responsibilities and traditions of the office stem from the creation of the contemporary Polish state, and the office is defined in the Constitution of Poland. According to the Constitution, the president nominates and appoints the prime minister, who will then propose the composition of the Cabinet. Fourteen days following their appointment, the prime minister must submit a programme outlining the government's agenda to the Sejm, requiring a vote of confidence. Conflicts stemming from both interest and powers have arisen between the offices of President and Prime Minister in the past.