As an Ulsterman, McIlroy can choose between representing either Great Britain or Ireland in the Olympic Games and he delayed that decision after missing Rio 2016 due to concerns over the Zika virus.
But speaking to the Golf Channel in the Japanese capital ahead of the PGA Tour-sanctioned ZoZo Championship, the 29-year-old has opted to stick with the country he played for as a junior.
McIlroy is currently ranked two in the world and this year joined Tiger Woods and Jack Nicklaus as the only men to win four majors and 15 PGA Tour titles before turning 30.
"Once I had left not trying to upset anyone aside, it was actually a pretty easy decision. All I've done throughout my life was play golf for Ireland and why would that change?" - Rory McIlroy speaking to the Golf Channel
Tokyo set to welcome top-class fields
McIlroy followed Woods in stating that he would like to go for gold at the Kasumigaseki Country Club in Kawagoe, 30km northwest of Tokyo.
He said, "I’m excited to play the Olympics and call myself an Olympian. Coming to such a golf-crazy country like Japan helps.
"It’s a really good atmosphere and just being here this week and seeing the enthusiasm of the fans makes me look forward to coming back next year and playing the Olympics."
McIlroy's world ranking means he is almost certain to make the tournament with a place in the top 15 on 23 June 2020 guaranteeing him qualification.
For Woods, who said earlier in October that making Tokyo 2020 was "a big goal" for him, the picture is less certain.
A maximum of four golfers per country are allowed in the two 60-person events with Woods' victory at the ZoZo Championship - his 82nd PGA Tour title to tie Sam Snead's record - moving him up to sixth in the world rankings.
That leaves him in the fourth and final spot for Team USA with world number one Brooks Koepka leading the way.
So competitive is the race for Team USA spots that all four of their representatives at Rio 2016 - bronze medallist Matt Kuchar, Rickie Fowler, and major winners Bubba Watson and Patrick Reed - stand to miss out this time.
In fact, out of the current top 15 in the world, only defending champion Justin Rose competed in golf's return to the Olympics after a gap of 112 years.
Outside the top 15, a maximum of two golfers per nation are permitted depending on world rankings.
For everyone bar the United States, their top two ranked between 15 and 60 next June will be in the competition.
Right now, Britain would be the only other country to take up a full allocation of four thanks to the presence of Rose and Paul Casey inside the top 15 with Tommy Fleetwood 16 and three more players - including Rio 2016 competitor Danny Willett - in the top 30.
That means this year's Open champion Shane Lowry looks sure to join McIlroy in the Irish team with Austria's Bernd Wiesberger, Louis Oosthuizen of South Africa and Mexico's Abraham Ancer on track to make sure their countries are represented in Tokyo.
2016 Open champion Henrik Stenson is the top Swede in the rankings at 39 giving him the opportunity to go one better than his silver from Rio.
The hosts are guaranteed one spot which is occupied at present by Hideki Matsuyama with Shugo Imahira looking the most likely man to join him.
Australia could also have three representatives although that depends on whether Adam Scott can get back inside the top 15 with Marc Leishman and former world number one Jason Day the leading Aussies outside the bracket.
Sungjae Im and Byeong Hun An could make it two Koreans in the field with Canada's Adam Hadwin, Joaquin Niemann of Chile, Chinese Taipei's C.T. Pan and Thailand's Jazz Janewattananond all currently inside the qualification spots.
Top 15 in Men's Official Golf World Ranking (as at 27 October 2019):
1 Brooks Koepka (USA)
2 Rory McIlroy (IRE)
3 Dustin Johnson (USA)
4 Justin Thomas (USA)
5 Jon Rahm (ESP)
6 Tiger Woods (USA)
7 Patrick Cantlay (USA)
8 *Justin Rose (GBR)
9 Xander Schauffele (USA)
10 Bryson DeChambeau (USA)
11 Francesco Molinari (ITA)
12 Paul Casey (GBR)
13 Webb Simpson (USA)
14 Tony Finau (USA)
15 Gary Woodland (USA)
Olympians denoted by *
Double major winner Ko leads women's line-up
When women's golf made its first Olympic appearance since 1900, Lydia Ko was the favourite for gold.
The New Zealander delighted the galleries with a hole-in-one, but had to settle for silver.
For Tokyo 2020, a woman named Ko will almost certainly be favourite again although this time it will be South Korea's Ko Jin-young.
The winner of two majors in 2019 in just her second season on the LPGA Tour, 24-year-old Ko is well clear in the rankings and heads a number of Koreans vying for Olympic qualification.
Just as with the Americans in the men's competition, being in the top 15 won't be enough to secure a berth in Tokyo with Rio 2016 champion Inbee Park the fourth-highest Korea in 10th place.
In May, Park told Korean news agency Yonhap she would be keen to defend her crown but knows doing so will be far from easy after returning from a career slump to be victorious in Brazil.
She said, "When the Rio Olympics ended, I thought the next Olympics four years later were too far off. I doubted whether I could be still active until then. But as the next Olympics is getting closer, I think it is worth a try.
"I know making it to the national team is harder than winning the Olympic gold. I would be very pleased to have a chance to play at the Olympics and defend my title." - Inbee Park speaking to Yonhap
Kim Sei-young, tied for 25th in Rio, currently stands to miss out in 14th with Ryu So-yeon and Kim Hyo-joo right on the fringe.
Nasa Hataoko is the top Japanese in the rankings at number three with Olympians Lexi Thompson, Brooke Henderson, Minjee Lee and Ariya Jutanugarn leading the way respectively for USA, Canada, Australia and Thailand.
Two-time major winner Jutanugarn, who could be joined by older sister Moriya in Tokyo, led after the first round in Rio but was forced to withdraw in round three with a knee injury.
There are currently four Americans in the top 15 including sisters Nelly and Jessica Korda.
At 21, Nelly is the younger daughter of former Australian Open champion Petr Korda and another Czech tennis player, Regina Rajchrtova.
She has really shone in the last year, winning two LPGA Tour titles and eclipsing her 26-year-old sister's best career ranking of eight.
Both sisters excelled in the recent Solheim Cup in Scotland, scoring 3.5 points apiece, although that was not enough to prevent Europe taking the trophy.
Just one of Europe's winning team at Gleneagles - Spain's Carlota Ciganda - is currently in the world's top 15.
Ciganda finished tied for 39th at Rio 2016 but has had her best major performances in the last 18 months.
The next highest European is Englishwoman Bronte Law who scored her first PGA Tour victory in May at Kingsmill in Virginia.
Charley Hull - tied seventh in Rio - and 2018 British Open champion Georgia Hall look set to fight it out with Law for two spots for Britain in Tokyo.
Top 15 in Women's World Rankings (as at 28 October 2019):
1 Ko Jin-Young (KOR)
2 Park Sung-hyun (KOR)
3 Nasa Hataoka (JPN)
4 Lee Jeong-eun (KOR)
5 *Lexi Thompson (USA)
6 *Brooke Henderson (CAN)
7 Danielle Kang (USA)
8 Nelly Korda (USA)
9 *Minjee Lee (AUS)
10 *Ariya Jutanugarn (THA)
11 *Inbee Park (KOR)
12 Hinako Shibuno (JPN)
13 *Kim Sei-young (KOR)
14 *Carlota Ciganda (ESP)
15 Jessica Korda (USA)
Olympians denoted by *