Montpellier were crowned champions after beating relegated Auxerre 2-1 to finish the season on 82 points, three points ahead of big spending Paris Saint-Germain.
The match, however, ended almost two hours and 30 minutes after it kicked off.
"That's it, we did it," Girard told reporters.
"When it goes down this way, you are worried, you wonder how it is going to end up. But better late than never. At some point I asked the referee if we could play until 5am."
Angry Auxerre fans threw tennis balls, toilet paper, tomatoes and then flares onto the pitch, causing three interruptions and anti-riot police to be sent in the stands to restore order.
On the pitch, Nigeria's John Utaka scored Montpellier's two goals to cap the southerners' remarkable season.
"I am very proud of the lads, it was an outstanding season. We deserved to go all the way, the lads are so young and they kept their cool," said Girard.
"It was possibly the longest game I ever 'played'," he added.
"We play football to live these kind of moments. It's outstanding, it's huge," said Olivier Giroud, who finished joint top scorer with PSG's Nene on 21 goals.
"I don't even know if we're going to sleep this week.
"This title rewards the whole squad, but also the club, the region."
Midfielder Karim Ait Fana said doubt had crept into the team when Auxerre went ahead in the first half through Olivier Kapo's header from a Roy Contout corner.
"We started to doubt when Auxerre scored the opener. It was tough but we managed to control the game," he said.
"It's a season to remember."
Montpellier responded and marched to victory, providing inspiration for other small budget teams hopeful of upsetting better-funded opponents.
"It's good for our football. It shows you should not fear anyone and always give your best," said Girard, who was quick to turn his sights towards next season, when Montpellier will play in the Champions League for the first time.
"It would be great to keep the same squad and make a couple of changes to be really competitive."
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