The American duo won 5-7, 6-1, 13-11 as they added the season-ending crown to the Wimbledon and US Open titles.
With three Masters tournaments and two Grand Slams in the space of seven weeks, players might have to make hard choices but French Open director Guy Forget is confident they will turn up at Roland Garros.
It was Halep's second Grand Slam title following her triumph at Roland Garros in Paris last year.
'I'm writing this to say I'm not going to do any press during Roland Garros,' Osaka tweeted
Djokovic will need to win in Tokyo and then the US Open later this year to achieve the feat that has so far only been accomplished by Steffi Graf in 1988.
Czech fourth seed Tomas Berdych bulldozed his way into the second round of the French Open by thrashing Japanese qualifier Yoshihito Nishioka 6-0, 7-5, 6-3 on Monday.
It was only his second defeat in 11 years and 72 matches at Roland Garros, yet it came as little surprise for Rafael Nadal as the nine-time champion admitted he had his French Open quarter-final defeat to Novak Djokovic coming.
It took nearly five hours of gruelling tennis for Rafael Nadal to fend off Grigor Dimitrov and book a dream Australian Open final against Roger Federer but before Melbourne Park the Spaniard endured a season of heartache and doubt.
Ash Barty ended Australia's 44-year wait for a home winner at the Australian Open when the world number one staved off a fightback from American Danielle Collins to complete a 6-3, 7-6(2) win.
Barty's athleticism is remarkable.
Australian Kyrgios was beaten in his first match in Lyon on Tuesday by Argentina's 94th-ranked Nicolas Kicker -- serving nine double faults during a 2-6, 6-4, 6-2 defeat.
Twice former champion Rafael Nadal will not play at this year's Wimbledon due to the wrist injury that forced the Spaniard out of the French Open, he said on Thursday.
Cecchinato in 'dreamland' after stunning David Goffin on Sunday
Cilic had never made it past the quarters in Paris but has now made the semis or better at all four majors.
Fourteen-time Grand Slam champion Rafael Nadal on Wednesday pulled out of the Queen's club grass-court tournament, due to wrist injury.
Wimbledon officials on Tuesday said they are continuing plans for the grasscourt major to start on June 29 as scheduled even though French Open organisers postponed the claycourt Grand Slam to September due to the coronavirus pandemic.
Australian controversial tennis star Nick Kyrgios has been slapped with the largest fine at the French Open for uttering an audible obscenity during his third round loss to Richard Gasquet.
The signs that things were going horribly wrong for Roger Federer were laid bare at Roland Garros.
Up to 60% of usual capacity will be allowed to attend 2020 French Open, say organisers
Penpix of the top men's contenders at the 2017 French Open:
Yannick Noah is looking to restore old-fashioned values to the French Davis Cup team as he embarks on his third stint as captain.
Eighth seed Barty joins 1969, 1970 and 1973 champion Margaret Court and 1971 winner Evonne Goolagong-Cawley on the list of Australian women who have lifted the trophy here in the professional era.
A quick look at Rafael Nadal's domination of Roger Federer at Roland Garros.
Man of many faces, Medvedev now a Grand Slam finalist
'And for me to just be hitting a tennis ball in the United States right now and have people come and watch me play ... I would want to be myself in this situation rather than anyone else in the world.'
'But in mid-October, if we're able to come together and we've been able to provide revenue for 600 people, I think we will be very satisfied as a federation and I as a former player.'
Second seed Novak Djokovic tackles Croatia's Marin Cilic in the third round of the French Open on Friday as his attempt to win the only grand slam title to elude him gathers pace.
The 12-time French Open champion unhappy with schedule.
Naomi Osaka is also the first woman to win a second Slam immediately after her first since Jennifer Capriati in 2001 but her meteoric rise has been followed by a distinct dip ahead of Roland Garros.
Japan's Osaka ended the stand-off with the French tennis federation (FFT) by withdrawing from the claycourt major
Federer had his first hit on Thursday at the ATP 500 event at the German city of Halle, where he has won 10 titles.
Serena Williams overcame a gritty challenge from unseeded Dutchwoman Kiki Bertens, winning 7-6(7), 6-4, to reach the French Open final, in Paris, on Friday. She will meet Garbine Muguruza, who reached her second Grand Slam final when she beat Australia's Samantha Stosur 6-2, 6-4 in the first semi-final at Roland Garros.
Roger Federer's struggles continued when he was beaten 7-6 (2), 6-4 by fast-rising Austrian Dominic Thiem in the third round of the Italian Open in Rome, on Thursday.
Images from the matches played on Day 8at the Roland Garros on Sunday
Novak Djokovic was unexpectedly beaten by fifth-ranked Alexander Zverev, quashing his hopes of winning an Olympic singles gold medal, the only major honour missing from his long list of accolades.
Maria Sharapova claimed her second French Open title when she floored Romanian fourth seed Simona Halep 6-4, 6-7(5), 6-4 after a marathon encounter in Saturday's final.
Factbox on Austria's Dominic Thiem, who beat German Alexander Zverev 2-6, 4-6, 6-4, 6-3, 7-6(6) to win the US Open title on Sunday.
Sam Stosur powered into the French Open quarter-finals with a 7-6(0), 6-3 win against Simona Halep in Paris on Tuesday, adapting better to damp and heavy conditions than her higher-ranked Romanian opponent.
'I think it's (pressure) maybe because I haven't played in an Olympics before and for the first one to be here was a bit much.'
It will be the second time Nadal and Del Potro meet at Roland Garros. The previous match up saw the Spaniard beat Del Potro in straight sets in the opening round in 2007.