Lech Kaczyński, Polish lawyer and politician, 4th President of Poland (d. 2010)
Lech Aleksander Kaczyński (Polish pronunciation: [ˈlɛx alɛkˈsandɛr kaˈt͡ʂɨj̃skʲi] (listen); 18 June 1949 – 10 April 2010) was a Polish lawyer and politician who served as the Mayor of Warsaw from 2002 until 2005, and as President of Poland from 2005 until his death in 2010. Before his tenure as president, he previously served as President of the Supreme Audit Office from 1992 to 1995 and later Minister of Justice and Public Prosecutor General in Jerzy Buzek's cabinet from 2000 until his dismissal in July 2001.

Born in Warsaw, he starred in a 1962 Polish film, The Two Who Stole the Moon, with his identical twin brother Jarosław. Kaczyński was a graduate of law and administration of Warsaw University. In 1980, he was awarded his Ph.D. by Gdańsk University. In 1990, he completed his habilitation in labour and employment law. He later assumed professorial positions at Gdańsk University and Cardinal Stefan Wyszyński University in Warsaw.

During the communist period, Kaczyński was an activist in the pro-democratic anti-communist movement in Poland, the Workers' Defence Committee, as well as the Independent Trade Union movement. In August 1980, he became an adviser to the Inter-Enterprise Strike Committee in the Gdańsk Shipyard and the Solidarity movement. After the communists imposed martial law in December 1981, he was interned as an "anti-socialist element". After his release, he returned to trade union activities, becoming a member of the underground Solidarity. When Solidarity was legalized again in the late 1980s, Kaczyński was an active adviser to Lech Wałęsa and his Solidarity Citizens' Committee in 1988.

From February to April 1989, he participated in the Polish Round Table Talks along with his brother. After Solidarity's victory in the 1989 Polish legislative election, Kaczyński became a senator and vice-chairman of the movement. Then in the 1991 Polish parliamentary election, he was elected into the Sejm as a non-party member. He was also the main adviser and supporter of Lech Wałęsa when the latter was elected President of Poland in December 1990. Wałęsa nominated Kaczyński to be the Security Minister in the Presidential Chancellery but fired him in 1992 due to a conflict concerning Jan Olszewski's government. In 2003, Kaczyński co-founded the Law and Justice party, after splitting from the Solidarity Electoral Action and the Christian National Union, along with his brother. Kaczyński was the party's presidential candidate, during the 2005 Polish presidential election. In the first round of voting, Kaczyński received 33.1% of the valid votes. In the second round of voting, Kaczyński received 54.04% of the vote, defeating Donald Tusk, who received 45.96% of the vote. He was sworn in as president on 23 December 2005.

On 10 July 2006, Kaczyński appointed his brother as Prime Minister of Poland upon the resignation of Kazimierz Marcinkiewicz, the brothers then became the first pair of brothers in the world to serve as president and Prime Minister of a country and the only twin brothers to do so, until 2007, when his brother lost the parliamentary election on 21 October 2007, finishing a distant second behind the conservative-liberal party Civic Platform. His brother was succeeded as prime minister by his former presidential rival Donald Tusk. On 10 April 2010, Lech Kaczyński was killed, along with his wife, in the crash of a Polish Air Force jet that occurred on a landing attempt at Smolensk North Airport in Russia. He was the first Polish president to die in office since the assassination of Gabriel Narutowicz.