| Wilhelm Kaisen | |
| Party: | Social Democratic Party |
| Deputy1: | Jules Eberhard Noltenius Adolf Ehlers Willy Dehnkamp |
| Office1: | President of the Senate and Mayor of Bremen |
| Predecessor1: | Erich Vagts |
| Successor1: | Willy Dehnkamp |
| Birth Date: | 1887 5, df=yes |
| Birth Place: | Hamburg, German Empire |
| Death Place: | Bremen, West Germany |
| Spouse: | Helene Kaisen |
| Children: | 4 |
| Term Start1: | 1 August 1945 |
| Term End1: | 17 July 1965 |
Carl Wilhelm Kaisen (22 May 1887 – 19 December 1979) was a German politician from the Social Democratic Party of Germany (SPD) who served as the 2nd President of the Senate and Mayor of Bremen from 1945 to 1965. In 1958/59 he served as the 10th President of the Bundesrat. He became a symbolic figure of the German reconstruction in Bremen after 1945.
Kaisen was born in the German city of Hamburg, and spent his youth there. His family's poverty did not allow him to visit a higher school or even receive a high school education. In 1905 he became a member of the SPD. After World War I, he moved to his wife's home city of Bremen. Influenced by his family, he got the SPD into the parliament of Bremen (Bürgerschaft). From 1919 to 1928 he was a journalist and editor-in-chief of the SPD newspaper . From 1920 to 1928 he was member of the Bürgerschaft. In 1928, Kaisen became the SPD Senator of Social Services in the Senate of Bremen. In March 1933, he was pressured to resign by the Nazis.
Kaisen was not involved in politics during the Nazism era. He spent his time with agricultural work in the suburb of Bremen-Borgfeld.
On 1 August 1945, the US military government made Kaisen mayor of Bremen. Supported by the Liberals as well as the Communists he tried to re-establish the political and economical structures of the Weimar Republic. He was re-elected by the people of Bremen during the first free elections after the war. In July 1965, after nearly twenty years in office, he resigned as mayor.
Kaisen was very popular with the general public, but less so within the SPD itself. His support for the decision to position Germany within NATO led to a break with SPD chairman Kurt Schumacher.
Kaisen died in Bremen on 19 December 1979.
Although not well known in the rest of Germany, Wilhelm Kaisen is held in high regard in Bremen and Bremerhaven. A number of things were named in his honor:
There are also several streets and squares in both cities named after Kaisen and his wife. There is also a Wilhelm Kaisen state at Herdentor near Bremen central station and aWilhelm Kaisen bust, which is located in Borgfeld, a north-eastern district of Bremen.