Oenning sacked after poor Hamburg start
Hamburg have taken just one point from their opening six games, with the latest defeat coming on Saturday at home to Borussia Monchengladbach.
Oenning's dismissal comes just a day after he was given a vote of confidence by the club's sporting director Frank Arnesen.
Arnesen said today: "Over the past two days, after the 1-0 defeat against Monchengladbach and after lots of intense discussion, we have come to the conclusion that we had to make that decision. We will now work hard to find a successor to Michael Oenning."
Reserve team coach Rodolfo Cardoso will take over on an interim basis. Oenning said: "It is understandable for me that the club, given the current situation, would like to go in a different direction."
Hamburg were busy in the transfer market over the summer, replacing established players like Ruud van Nistelrooy, Ze Roberto, Eljero Elia, Piotr Trochowski and Joris Mathijsen with a host of untried youngsters.
A 3-1 defeat at defending champions Borussia Dortmund on the opening weekend set the tone and a 5-0 thrashing at Bayern Munich followed a fortnight later. Home defeats to Cologne and, at the weekend, Monchengladbach proved the final straw.