Businessman Dejphon Chansiri, whose family owns Thai Union Frozen Group, has acquired a 100 percent stake in the Championship (second tier) club.
The club confirmed the takeover on their website (www.swfc.co.uk) on Thursday with local media reports saying the buyout cost around 30.0 million pounds ($45.40 million).
Outgoing chairman Milan Mandaric, who has been in charge since December 2010, confirmed earlier this month the club were in talks with potential investors.
"Once the final details and Football League approval have been concluded I will step down as chairman and as a director. In my four years in Sheffield I have come to regard this city as my home," Serb-American Mandaric told the website.
Saying he would happily assist the new owners in an advisory role, he added: "I desperately (still) want to be a part of the journey we all started together when I arrived which I am sure will ultimately see our club back in the Premier League very soon."
Chansiri, who watched Wednesday's 0-0 draw with Birmingham City from the directors box at Hillsborough on Tuesday, said: "I am very excited at the prospect of taking over control from Milan.
"I believe this club has huge potential and I can assure all our supporters that I will be working extremely hard to bring the success that I already sense from my short time in your city our supporters so desperately crave."
The deal remains subject to ratification by the Football League but Chansiri's involvement has already led to funds being made available to strengthen the squad.
Wednesday, formed in 1867, are the fourth oldest League club in England and have been English champions four times in 1903, 1904, 1929 and 1930 as well as winning the FA Cup three times in 1896, 1907 and 1935.
They are currently ninth in the Championship, nine points off the playoff places.
($1 = 0.6608 pounds)
(Editing by Pritha Sarkar)
