Rooney is a lifelong Republican who endorsed Obama during Pennsylvania's contentious Democratic primary last year and campaigned for him throughout the election. The president returned the favor by nominating him to the ambassador post, a move that had been the subject of almost fever-pitch speculation in Irish circles in recent days.

"I am honored and grateful that such a dedicated and accomplished individual has agreed to serve as the representative of the United States to the Irish people. Dan Rooney is an unwavering supporter of Irish peace, culture and education," Obama said in a statement.

The 76-year-old Rooney took over the presidency of the Steelers in 1975 and is a Hall of Fame owner. His team won this year's Super Bowl, shocking the Arizona Cardinals 27-23 on Santonio Holmes' tiptoe catch for a touchdown with 35 seconds to play.

Rooney has received the American Ireland Fund's lifetime achievement award.

The "Rooney Rule," which requires any team with a head coaching vacancy to interview at least one minority candidate, was developed by an NFL committee Rooney chaired.