Djokovic's challenger will be a 22-year-old who is bidding to become the first Greek to win a singles major.
Nadal, bidding for a record-extending 14th French Open title, won the first five games of the match as he looked on course to repeat his drubbing of the Serb in last year's final.
Just as against Swiss 20-time Grand Slam champion Federer in Saturday's semi-final, the 21-year-old produced a dashing display of power and guile to stun the in-form Djokovic 6-4, 6-3.
Marcin Matkowski and Mariusz Fyrstenberg beat fourth seeds Mahesh Bhupathi and Mark Knowles 6-4, 6-2 in the final of the Madrid Masters.
Marin Cilic beat unseeded German Michael Berrer 6-4, 6-7, 6-3 on Sunday to win the Zagreb Indoors tournament for the second successive year and clinch his fifth career title.
Switzerland's challenge at the ATP World Tour Finals melted away like an Alpine glacier in a heatwave on Sunday as Rafa Nadal and Novak Djokovic marched on to the grand finale.
Matteo Berrettini won the Stuttgart Open for a second time after he beat Andy Murray 6-4, 5-7, 6-3 on Sunday to deny the Scot what would have been his first title on grass in six years.
18-year-old Carlos Alcaraz earned his first ATP Masters 1000 crown
Rafael Nadal is the oldest title winner in the history of the clay-court tournament.
Simona Halep will take over as the new number one in the WTA world rankings after progressing to the China Open final with a dominant 6-2 6-4 victory over Latvia's Jelena Ostapenko in Beijing on Saturday.
US Open champion Carlos Alcaraz has become the youngest world number one since the ATP rankings began in 1973.
Novak Djokovic will begin his Australian Open title defence against Frenchman Jeremy Chardy, while reigning women's champion Sofia Kenin meets wild card Maddison Inglis, following the draw for the year's first Grand Slam on Friday.
Leander Paes and Matthew Ebden continued their winning streak, beating Jonathan Erlich and Andrei Vasilevski 6-4, 3-6, 10-7 to enter the doubles final at the $1,62,000 Bengaluru Open ATP Tennis Challenger, in Bengaluru, on Friday.
Unheralded Igor Kunitsyn upset former world number one Marat Safin 7-6, 6-7, 6-3 in an all-Russian Kremlin Cup final to clinch his maiden title.
The former world No.1 doubles pair upset fourth seeds Mark Knowles of Bahamas and Daniel Nestor of Canada in the semi-finals of the ATP Masters.
A round-up of all the tennis action from around the globe.
Monfils, 35, reached the last four at the 2008 French Open and repeated the feat eight years later at the 2016 US Open but has never reached a Grand Slam final.
A summary of sports events and sports persons, who made news on Tuesday
Rohan Bopanna and Aisam-ul-haq Qureshi missed out on capturing their second ATP title of the season after losing the fiercely fought final of the St. Petersburg Open to Daniele Bracciali and Starace Potito, at St.Petersburg.
'This has been an emotional week and I want to thank everyone for the outpouring of support.'
World number one Novak Djokovic overpowered Dennis Novak after Dusan Lajovic battled past Gerald Melzer and Serbia went on to a 3-0 win in their opener against Group F hosts Austria in the Davis Cup Finals in Innsbruck on Friday.
Roger Federer's late bid to secure his customary place in the season-ending ATP World Tour finals began with a routine opening round win over Adrian Mannarino in his home town tournament in Basel on Monday.
For all his renowned mental strength it was psychological exhaustion that made Rafael Nadal consider skipping the season-ending ATP World Tour finals this year, the 14-times grand slam champion said on Tuesday.
Another Indian pair of N Sriram Balaji and Vishnu Vardhan will also be seen in the semi-finals after their opponents, Gianluca Mager and Emil Ruusuvuori withdrew from the last-eight match due to an injury to the former.
Top seed Janko Tipsarevic of Serbia lived dangerously before making the final with a confident 6-1, 6-4 triumph over qualifier Go Sodea of Japan in the semi-final of the ATP Tour $450,000 Chennai Open Tennis championship on Saturday.
While Djokovic has a firm grip on top spot, there will be a new number two on March 15 in Russian Daniil Medvedev, who will climb one place to his career-best ranking to replace Nadal, who has not played since the Australian Open due to a back injury.
Djokovic says Peng situation horrifying, says tennis must unite.
Rafael Nadal delved deep into his seemingly inexhaustible reserves of willpower on Saturday to fight off Andy Murray in a three-hour classic and reach the final of the ATP World Tour Finals for the first time.
American Andy Roddick has booked his place at the World Tour Finals with four weeks of the season remaining, the ATP said on Tuesday.
Russian qualifier Daniil Medvedev stunned home favourite Kei Nishikori in Tokyo on Sunday, winning the final of the Japan Open 6-2, 6-4 in just over one hour.
World number one Novak Djokovic had to work hard for a three-set victory over Hungarian Marton Fucsovics at the Paris Masters on Tuesday in his first match since losing the U.S. Open final in September.
Nagal's court coverage and solid defence in long drawn points was the highlight of his win.
Davis Cup: Strong Indian team is firm favourite against Pakistan in historic clash
Leander Paes and Stanislas Wawrinka shocked 2014 Wimbledon champions Vasek Pospisil and Jack Sock 7-6(4), 3-6, 10-3 to make it to the doubles quarter-finals at the ATP Masters Western and Southern Open, in Cincinnati, on Tuesday.
Rafael Nadal will become the first man to win 21 Grand Slam titles if he defeats the Russian in Melbourne.
Aryna Sabalenka rose above geopolitical tumult to become the first player to claim a Grand Slam title as a neutral at the Australian Open.
American teenage sensation Coco Gauff progressed to her maiden WTA final as she eased past Germany's Andrea Petkovic 6-4, 6-4 at the Linz Open on Saturday. The 15-year-old Gauff became the youngest player to reach a WTA final since Czech Republic's Nicole Vaidisova won the Tashkent Open in 2004, also aged 15.
Rohan Bopanna and Prakash Amritraj crashed out in their respective men's singles semi-final matches at ATP Challenger Series tournaments being simultaneously played in England and the United States.
After shaking hands with the opponents, the 24-year-old Zverev, ranked third in singles, approached the umpire's chair and hit it repeatedly before heading towards his courtside seat, upset over a line call during the match earlier.
Andy Murray battled past Romanian qualifier Marius Copil 6-3, 6-7(7), 6-4 at the European Open in Antwerp on Friday to reach his first singles semi-final in two years.