Rafael Nadal racked up his 80th French Open win, while Maria Sharapova battled back from a final set deficit to reach the second round as Serena Williams made her eagerly-awaited Roland Garros return to Grand Slam tennis on Tuesday.

Nadal, the 10-time champion, defeated Italian lucky loser Simone Bolelli 6-4, 6-3, 7-6 (11/9).

World number one Nadal had been two sets up but 0-3 down in the third when rain caused the tie to be suspended late Monday.

He quickly levelled at 3-3 on Tuesday, saved four break points in the eighth game before saving four set points in the breaker.

The top seed eventually claimed victory on a third match point when Bolelli dumped a forehand into the net.

Nadal, bidding for an 11th title in Paris and his 17th major, next faces Argentina's Guido Pella for a place in the last 32.

"I really suffered today but it was a good test," said Nadal who had been in danger of dropping his first set at Roland Garros since his 2015 quarter-final loss to Novak Djokovic.

"Simone is a very good player and he had lots of chances and was very agrressive."

Two-time champion Sharapova survived a serious scare to claim a 6-1, 4-6, 6-3 victory over Dutch qualifier Richel Hogenkamp, ranked 130, in her first French Open match since 2015.

The Russian was not given a wildcard by organisers for the tournament last year, which took place shortly after her return from a 15-month doping suspension.

Sharapova, the 28th seed, will face Croatia's Donna Vekic in the second round.The 31-year-old, five-time major champion, took just 24 minutes to win the first set of a match which was delayed from Monday due to thunderstorms, but threw away a 3-1 lead in the second.

Sharapova was staring down the barrel of falling at first hurdle in a Grand Slam tournament for the first time since the 2010 Australian Open when trailing 3-0 in the third, but the former world number one dug deep and reeled off six straight games to edge into round two.

The Russian, who was Paris champion in 2012 and 2014, fired 35 winners in her victory on Court Suzanne Lenglen.                  - Serena returns -                                    Williams returns to Grand Slam tennis for the first time since the 2017 Australian Open where she won a 23rd major while also being two months pregnant.

The 36-year-old's return comes with the great American ranked at a lowly 451, a consequence of her lengthy absence from the tour after giving birth to her daughter in September.

Williams has played just four matches in 2018, the last of which was a first-round exit to Naomi Osaka in Miami.

Three of her Slam titles have come in Paris -- in 2002, 2013 and 2015 -- and longtime coach Patrick Mouratoglou has no doubt that Williams is capable of adding a fourth.

"Can she do it? Serena can achieve anything -- after being her coach for six years, I'm even more sure of that statement," said the Frenchman.

Williams starts her 16th Roland Garros against Czech world number 70 Kristyna Pliskova who has never won a match at the tournament in three visits.

Third seed Marin Cilic reached the second round with a 6-3, 7-5, 7-6 (7/4) win over Australia's James Duckworth.

Wimbledon and Australian Open runner-up Cilic, 29, fired 47 winners and 13 aces past the 1,072nd-ranked Duckworth who was playing his first match since the 2017 Australian Open.

Canadian teenager Denis Shapovalov eased to a 7-5, 6-4, 6-2 victory over Australian John Millman in his first ever main-draw French Open match.

The 19-year-old, who lost in Roland Garros qualifying last year but is now the 24th seed, will next take on German world number 70 Maximilian Marterer for a place in the last 32.

"The last couple of weeks I've been playing unbelievable on this surface," said Shapovalov, the youngest player to break into the world's top 30 since 2005.

Third seed and 2016 champion Garbine Muguruza defeated 2009 winner Svetlana Kuznetsova 7-6 (7/0), 6-2.

Spain's Muguruza next faces French wildcard Fiona Ferro, ranked 257, for a place in the last 32.

With the headlines dominated by the returns of Williams and Sharapova, world number one Simona Halep will begin her latest bid to win a maiden Slam very much under the radar.

The Romanian, who blew a set and 3-0 lead to lose the 2017 final to Jelena Ostapenko, faces Alison Riske, the 83rd-ranked American.