Rooney used a spectacular bicycle kick with his back to the goal for the 2-1 win over rival Man City.
The United and England striker leaped to meet a right-wing cross with an overhead strike that flew into the top corner after 77 minutes.
"I saw it coming over and I thought why not? Nine times out of 10 they go into the stand," Rooney told Sky Sports.
Wow....what a goal by ROOOOOOONEY!!! What a way to win the derby!!" he tweeted, before adding: "That bicycle kick was one dirty strike...POW...what a strike what a goal what a netbuster!!"
Even golfers Lee Westwood and Rory McIlroy, playing in the Dubai Desert Classic, commented. McIlroy simply tweeted; "BOOM!!!!!!!!"
Ferguson said the quality of the strike reminded him of United great Denis Law, who scored 171 goals in his stellar career at the club.
"It was stunning," Ferguson said. "We've had some fantastic goals here but in terms of execution ... you'll never see that."
Nani had given United a first-half lead with a neat control and finish, before City equalized with a deflected effort in the 64th.