Substitute Jesus lobbed the ball over Saints goalkeeper Alex McCarthy with virtually the last kick of the game at St Mary’s following a superb pass from Kevin De Bruyne.
The last-gasp goal — six years to the day since Sergio Aguero’s dramatic title-winning strike against QPR — sparked mayhem among City’s players and travelling support. And coach Guardiola hailed it as a fitting finale to a record-breaking campaign.
“100 points, still I cannot believe it,” said Guardiola. “100 points is a massive achievement.
“Of course nothing changed before or during the game (in terms of the title) so 97, 98 but we have to play for something.
“During the game we were focused and at the end an excellent pass from Kevin and amazing finish from Gabriel made the difference and achieved that record.
“100 points is a lot; 50 points at home, 50 points away so it means how stable, how good we were all the season.
“Our consistency once again showed up today and did it.
“A lot of goals, concede few, a lot of points, wins at home, wins away; everything was perfect this season and finished the way we deserved to finish.”
Formidable City set new records for points gained, goals scored and games won in a Premier League campaign by beating Brighton 3-1 on Wednesday evening.
Ahead of today’s title parade through the streets of Manchester, they looked to have been thwarted in their attempts to accumulate a century of points before the sensational climax on the south coast ensured those figures became 100, 106 and 32 respectively.
While Guardiola thinks it is unlikely his team can break their own records next season, he feels his players can still get better.
“Today, we only had two or three shots on target, we can shoot more,” he said.
“A team is individual players and always you can improve individual players so with that it makes sense to go to the training sessions and do it.
“When you analyse the numbers, I would say we can’t improve the numbers, no. We cannot be better in terms of numbers.
“In terms of playing football, yes.
“Because the players can do better, the manager as well, in a group, in a team we can do better.”
Despite yesterday’s narrow defeat, Southampton avoided an improbable relegation.
Only a highly unlikely 10-goal swing in goal difference could send them down and a loss for relegation rivals Swansea meant they were never in serious danger of the drop.
Saints manager Mark Hughes, appointed on a short-term contract last month, was pleased to complete the job of beating the drop after taking seven points from his final four games in charge.
“I should give myself a shake because I’m a little bit flat because I thought we could have won a game against the champions but it wasn’t to be,” said Hughes.
“You expect the best team in England to always go to the end and we ended up losing a game that I thought we possibly should have won but the bigger picture clearly was to make sure we got the job done today.
“People may say that I’ve done what I needed to do and well done Mark Hughes but credit all lies with the players.”
McCarthy, Cedric, Stephens, Yoshida, Hoedt, Bertrand (McQueen 81), Tadic, Hojbjerg, Romeu, Redmond (Ward-Prowse 64), Austin (Long 64).
Bravo, Danilo, Stones, Laporte,Delph (Gabriel Jesus 59), De Bruyne, Fernandinho, Gundogan (Foden 82), Sterling, Bernardo Silva (Diaz 78), Sane.