Europe defend the trophy won by Thomas Bjorn and his team at Whistling Straits in Wisconsin in September 2020 and it will be Harrington who will lead the team.
The three-times major victor, 47, will become the third player from Ireland - after Paul McGinley and Darren Clarke - to captain Europe in just four Ryder Cups.
'Obviously I'm thrilled to be named as Ryder Cup captain, it's not something I went into lightly, ' said the three-time major victor.
"Becoming captain is not something I went into lightly", Harrington said after he was appointed. I suppose you could look at this as being a natural progression, you move on from player to Vice Captain to Captain, but it's not something I take on without a certain amount of trepidation.
"He has done three vice-captaincies and I think he's ready for this job". For the best part of the next two years the 47-year-old will live and breathe the Ryder Cup.
Harrington spoke of finding that little edge to give Europe the best possible chance of retaining the trophy in Wisconsin, and he'll leave no stone unturned over the next 18 months or so.
Harrington played in the biennial event in six consecutive contests, including winningm teams in 2002, 2004, 2006 and 2010.
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"I think it will mean a lot, it's a great honour for him", two-time Ryder Cup player Des Smyth told RTÉ Sport.
"I have the support of the players, then it really came down to whether I wanted to be in the hat".
Harrington will remarkably become the third Irish-born European Captain in the past four Ryder Cup's after Paul McGinley captained the victorious 2014 European Team at Gleneagles and with Darren Clarke captaining hapless 2016 side that lost at Hazeltine.
Harrington's seemingly only rival ahead of Tuesday's 1pm (UK time) announcement is Paul Lawrie but with both McGinley and Clarke as two on the five-man voting panel it was always be Harrington.
"The players want continuity, it makes my job easier that I have their confidence, they've spoken to me publicly and privately".
But, from a European perspective, I'm thoroughly looking forward to seeing how Harrington handles himself, and the great thing about him is that he will never hide.
"And secondly the course is a European-style of course, it's windy and has a links-feel to it". Thankfully we are going to Whistling Straits which is just a strong golf course.
"This is a one-time-only effort and that probably even makes the Ryder Cup captaincy extraordinary".