While Harrington was the obvious candidate to captain Europe in 2020, the Team USA captaincy is less clear-cut, although Wisconsin native Steve Sticker seems to be the popular choice.
The three-times major victor had been the clear favourite to succeed Denmark's Thomas Bjorn for the defence at Whistling Straits, Wisconsin, after having served as vice-captain at the last three Ryder Cups.
The 47-year-old joins Paul McGinley (2014) and Darren Clarke (2016), as professionals from the island of Ireland to lead Europe and will be hoping to emulate the last European triumph on American soil - at Medinah in 2012 - as Europe defend the trophy won memorably at Le Golf National last September.
Harrington, the third Irish captain of the Europe team in the last four stagings of the match, said he had a busy 18 months ahead and meant to make his captaincy a mix of all those he had served under.
"It's something I did think long and hard about", Harrington said during a press conference to announce his appointment at the European Tour's headquarters at Wentworth.
"I'm well aware that it's win or nothing, that's the way it goes". "I've actually learned a lot more as vice-captain than you do as a player".
"I want to hopefully leave the European Tour and Ryder Cup in a better place after two years".More news: North Korea's Kim Jong-un Reportedly Leaves Beijing by Personal Train
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Team Europe have dominated the Ryder Cup in recent years, winning nine of the last 12 biennial contests.
Padraig made six Ryder Cup appearances as a player, but being a vice-captain for the last three will be more important for him in his new role. "In light of the beating suffered by Darren Clarke in Minnesota in 2016, he knows that he faces ominous odds on a tricked-up links course that will be created to suit the Americans" longest hitters.
"The players want continuity, it makes my job easier that I have their confidence, they've spoken to me publicly and privately".
"I have had a successful career, and you want to always be successful in the golfing sphere because of what I've done", he said.
The US have not named their next captain.
Justin Rose, who was part of Bjorn's victorious team in France, was among those who also offered their congratulations, along with one of Harrington's ex-Ryder Cup colleagues Luke Donald. Thankfully we are going to Whistling Straits which is just a strong golf course.
"I know there's words there, but the actions nowhere near match up". Even mentioning a cup of coffee has been known to tip him into angst about how best to make one.