Rainer Michael Müller (born 9 December 1964) is a German politician of the Social Democratic Party (SPD) who served as Governing Mayor of Berlin from 2014 to 2021.

One of his most extensive projects, which planned to build business space and apartments on the grounds of the former Tempelhof Airport, was rejected in 2014 by a clear majority of Berlin citizens in a referendum.

After the election, Müller ended the grand coalition with the Christian Democratic Union and formed a new government with the Green Party and the left-wing Die Linke.

In the negotiations to form a coalition government under the leadership of Chancellor Angela Merkel following the 2017 federal elections, he was part of the working group on urban development, led by Bernd Althusmann, Kurt Gribl and Natascha Kohnen.

[citation needed] He has also been chairing a study commission set up to investigate the entire period of German involvement in Afghanistan from 2001 to 2021 and to draw lessons for foreign and security policy in future.