Chairman Darragh MacAnthony has finally completed his takeover of Peterborough from previous owner Barry Fry.
The Irish businessman, 31, first took the helm at Posh back in September, having decided to invest in the club.
But he was unable to become sole owner until a dispute with Peterborough's landlords was resolved.
MacAnthony has so far pumped in more than £5m into the club and has assembled the most expensive Posh squad in Football League history.
He has set manager Darren Ferguson a target of Premier League football in five years and the season started well for the League Two title favourites with a 3-0 win over Rochdale on Saturday.
MacAnthony said in a club statement: "This morning I officially became the owner of Peterborough United FC, 12 months after first arriving on the scene.
"Both myself and Barry sat down this morning for the official signing and it is all done and dusted, as I always knew it would be.
"My ultimate goal is one of reaching the highest level and giving the city of Peterborough a football club they can be proud of - on the pitch and off it."
Fry, also a former manager of Posh, remains as director of football at London Road.