The embassy in Dublin says the 80-year-old Rooney resigned Friday and returned to the United States. Press officer John Murphy said Rooney met with Irish Prime Minister Enda Kenny and President Michael Higgins during a final round of engagements this week.
Foreign Minister Eamon Gilmore hosted a farewell dinner for Rooney on Wednesday, but news of his imminent departure was kept secret, even though the resignation had been expected for some time. Murphy said the ambassador met embassy staff on Friday morning for goodbyes before heading to Dublin Airport for a flight to Pittsburgh.
Rooney, the grandson of an Irish immigrant, supported Obama in the 2008 Democratic primary and then campaigned for him.
In an op-ed published Friday in The Irish Times and the Pittsburgh Post-Gazette, Rooney said the relationship between the U.S. and Ireland is as strong as ever. He says the countries' common heritage and values creates a "shared kinship."
"I arrived in an Ireland that was starting to feel the effects of the global economic crisis. Over the following three years I would travel to every county meeting people from every part of Ireland and every walk of life and developed a deeper respect for the determination of the people to succeed in the face of hardship," Rooney wrote.
It's not clear what future role Rooney will have with the Pittsburgh Steelers.
His son and team president Art Rooney II told the Pittsburgh Tribune-Review that "we really haven't talked about what he wants to do when he gets back. We'll talk about that after the season."
On Saturday, Rooney and his wife Patricia reportedly plan to attend a memorial service in Milton, Mass., for their daughter Rita, who died Dec. 1.