Simon eventually prevailed in the third round encounter over Monfils 6-4, 6-4, 4-6, 1-6, 8-6 in four hours and 43 minutes and his reward will be a fourth round clash with reigning US Open champion and world No. 4 Andy Murray.
It did cap off a super Saturday for France in the third round of the Australian Open, though, after Jeremy Chardy upset Juan Martin Del Potro 6-3, 6-3, 6-7, 6-3, Jo-Wilfried Tsonga beat Blaz Kavcic 6-2, 6-1, 6-4 and Richard Gasquet downed Ivan Dodig 4-6, 6-3, 7-6, 6-0.
However, one Frenchman was always going to be eliminated on Saturday night on Hisense Arena, but nobody could have imagined it would take almost five hours and well past midnight for it be decided who that would be.
Certainly after the first two sets nobody would have predicted a marathon was in the making either when Simon took both of them 6-4. However, the fact that they were so tight and lasted 58 and 56 minutes respectively should have been a sign of what was to eventuate.
Monfils hit back winning an equally tight third set 6-4, but then he became the first player to significantly outplay the other when he dominated the third winning it 6-1.
Monfils then had all the momentum, but Simon had his equal desire and that led to a fifth set that lasted 94 minutes until Simon eventually broke through to win it eight games to six.
It brought to an end a brave comeback from two sets to love down from Monfils, but the former world No. 7 who currently sits at 86 will take great heart from his performances in Melbourne as he prepares for a big comeback year after an injury-ravaged 2012.
Simon is seeded 14th at the Australian Open but it will now take a massive effort for him to take it up to Murray on Monday after such a gruelling encounter, and also hurting his elbow in the process.
However, if he is able to beat Murray it would equal his quarter-final performance of 2009 at the Australian Open, which was his best Grand Slam result. The 28-year-old knows it will be tough to recover though.
"I will need to recover from this one before I think about Andy. I was almost dying at the end of the second set and it was everywhere by the end, that was the problem," Simon said.
"It (elbow) was cramping every time I was trying to play fast so I was just trying to find my rhythm and just trying to make him work."
While Simon will take on Murray on Monday, his French comrades have big fourth round matches as well with Chardy to take on Italian Andreas Seppi, with Tsonga and Gasquet to battle one another for a spot in the quarter-final.