Klaus Wowereit is a German politician of the Social Democratic Party (SPD) and was the Governing Mayor of Berlin from 21 October 2001 to 11 December 2014. In 2001 state elections his party won a plurality of the votes, 29.7%. He served as President of the Bundesrat in 2001/02. His SPD-led coalition was re-elected in the 2006 elections; after the 2011 elections the SPD's coalition partner changed from the Left to the Christian Democratic Union. He was also sometimes mentioned as a possible SPD candidate for the Chancellorship of Germany (Kanzlerkandidatur), but that never materialized.

The governing mayor of Berlin is the head of government, presiding over the Berlin Senate. As Berlin is an independent city as well as one of the constituent states of Germany, the office is the equivalent of the ministers president of the other German states, except the states of Hamburg and Bremen, where the heads of government are called "First Mayor" and "President of the Senate and Mayor", respectively. The title Governing Mayor of Berlin is the equivalent of Lord Mayor in the meaning of an actual executive leader.