Christoph Ahlhaus, a 40-year-old centre-right politician, was appointed premier of the German state of Hamburg on Wednesday, replacing Ole von Beust, 55, who has retired, DPA reports.
Ahlhaus, whose title will be mayor of Hamburg, belongs to Chancellor Angela Merkel's Christian Democratic Union (CDU). He will be a key to Merkel's efforts to rebound from flagging voter support in Germany's affluent second-biggest city.
He was formerly the city-state's interior minister. The premiers of Germany's 16 states are major figures in federal politics and chair the upper house of the German parliament in one-year turns.
The CDU and the Greens, who rule the state in coalition, have 68 out of 121 seats in the state legislature. Ahlhaus was appointed mayor by 70, indicating at least two opposition deputies backed him.
Beust, respected nationally as a CDU liberal, announced in July that he had had enough of politics after nine years as mayor.
The CDU-Greens alliance has attracted international attention and is widely viewed as a testbed for a similar coalition at national level, an option that might be forced on Merkel if her current coalition partner, the Free Democratic Party (FDP), were to crash.
After his nomination, Ahlhaus had swiftly reassured doubting Greens that he would stick to environmentalist policies that were approved by Beust and set out in a coalition agreement between the parties. Among those policies is construction of a city tram system.