The Azerbaijani businessman, who also owns FC Baku and French club Lens, will take over from Milan Mandaric and is keen to return the Championship outfit to the Premier League
Mammadov – who also owns French club Lens and FC Baku in his homeland – sealed his deal to buy the Hillsborough outfit on Tuesday.
The new owner will replace chairman Milan Mandaric in charge of the club and immediately stated his desire to return them to the Premier League for the first time since 1999-00.
"I am immensely pleased and proud to have agreed a deal to buy this wonderful club," Mammadov told Wednesday's official website.
"I am a passionate football fan with enormous respect for English football. I have been looking at investing in England for some time but I was determined to find the right club.
"I am hugely ambitious and feel the Owls match my passion and desire for success and represent our motto of Azerbaijan - Land of Fire.
"I promise the supporters I will work extremely hard to bring the success everyone so rightly craves."
The deal still requires Football League ratification but Mandaric expressed his delight at the news and said he had delivered on his promise to the club's supporters.
"I am delighted to have concluded a deal with Hafiz, he is a true football man and I have no doubt whatsoever that I am handing over control to someone with a real passion for the game and the ability to carry on the work I started three years ago to return Sheffield Wednesday back to the top division of English football," Mandaric said.
"It’s something that the wonderful supporters of this club deserve having remained so loyal throughout the difficult times prior to my arrival.
"On my first day at the club I promised the supporters two things; firstly I would ensure that when I left we would be in far better shape than when I arrived and more importantly, that I would only hand over ownership when I found the right man for the club and I sincerely believe I have delivered on both undertakings."
Since their relegation from the top flight, Wednesday have dropped to the third tier twice since.
They finished 16th in the Championship last term, nine points above the relegation zone.