Jarosław Aleksander Kaczyński (born 18 June 1949) is a Polish politician. He co-founded the Law and Justice (PiS) party in 2001 with his twin brother, Lech Kaczyński, and has served as its leader since 2003. He served as Prime Minister of Poland from 2006 to 2007, and has twice held the post of Deputy Prime Minister of Poland, first from 2020 to 2022, and a second time from June to November 2023. He is considered to have been the eminence grise of Poland, when PiS formed the government in 2005–2007 and again in 2015–2023, with direct political influence over the prime ministers Kazimierz Marcinkiewicz, Beata Szydło and Mateusz Morawiecki.

Jaroslaw Kaczyński as a student took part in protest during the March 1968 political crisis. Subsequently, he became involved in the anti-communist opposition as a collaborator of KOR and KSS KOR. He took part in the protests in August 1980 when he was arrested, then joined the Solidarity movement. In 1982 he became a member of the Polish Helsinki Committee. He took part in the 1988 strikes.

In 1989, Kaczyński took part in the Round Table talks. In 1989–1991, he served as a senator. In 1990, he founded the Centre Agreement party, of which he served as leader until 1998. In 1990–91 he was head of the chancellery of President Lech Wałęsa. He served as a Member of Parliament from 1991 to 1993 and continuously since 1997.

In 2001 he co-founded the PiS party with his twin brother, Lech Kaczyński, of which he became leader in 2003. Running for PiS, he served as the prime minister of Poland from July 2006 to November 2007, while his brother was the president of Poland. After PiS's electoral defeat in 2007, Kaczyński was the main leader of the opposition during Civic Platform's governments. Following the death of his brother in a plane crash, Jarosław Kaczyński ran in the 2010 Polish presidential election, losing to Bronisław Komorowski.

Since the 2015 victories of PiS, both in the presidential and parliamentary elections, Kaczyński was considered to be the most powerful politician in Poland and one of the most influential European leaders.[2] In 2020, he was designated as the Deputy Prime Minister of Poland with oversight over the defense, justice and interior ministries. He resigned from the government in November 2023 after the Law and Justice (PiS) party failed to gain a majority of seats in the Sejm in the 2023 Polish parliamentary election.

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