Hamburg have made Bruno Labbadia their new head coach, the Bundesliga strugglers announced on Wednesday.
Labbadia, 49, returns for a second stint at Hamburg and becomes the club's fourth coach this season.
"Into the future with Labbadia," Hamburg said on their website. "HSV ends search for a new coach, and banks on a new impulse in the finish."
Labbadia has been handed a 15-month contract, regardless of whether he keeps the bottom-of-the-table club, who have been in the Bundesliga since its inception, in the league.
The club also announced that current coach Peter Knabel will return to his old position as the sporting director after overseeing two defeats in two games.
"We have decided to make this step, because we believe the coaching position is very important," CEO Dietmar Beiersdorfer was quoted in the official press release.
"In Bruno Labbadia we have signed a good coach who is experienced in the battle against relegation."
Labbadia, who coached Hamburg from the summer of 2009 to April 2010, said: "I expect total commitment and passion from everyone involved in the upcoming weeks. We need to return to winning ways soon."
The appointment of Labbadia also means that the links with coach Thomas Tuchel come to an end.
The former Mainz coach was tipped to take over Hamburg next season following a sabbatical this season.
"We held numerous talks, but we could not reach an agreement. That's why we have decided to end the talks," Beiersdorfer said.
With six games left to be played, Hamburg are last in the league standings.
They trail Paderborn in the relegation/promotion playoff place by two points, and are four behind Hannover, the first team outside the drop zone.
At the weekend, Hamburg travel to northern rivals Werder Bremen, who need all three points to stay in the race for Europa League.
Labbadia last coached in Bundesliga in August 2013, when he was sacked by Stuttgart following three defeats in the first three games of the season.
He is Hamburg's fourth coach of the season, following in the footsteps of Mirko Slomka, Joe Zinnbauer and Peter Knabel.