Pep Guardiola's side had already secured the record for most points in a single season in the English top flight heading into the final game at St Mary's.
Despite penning an initial six-year deal when he moved to England, City have seen fit to tie their number one down to renewed terms that run until 2025.
City also recorded the most wins in an English top-flight season with 32.
"I'm delighted to sign my new contract".
That's what BBC pundit and all-time Premier League goalscorer Alan Shearer believes.
"They have produced some football that we have never witnessed in the Premier League before".
The week after the upset at the hands of Jose Mourinho's men, the Blues wrapped up the title with five games to go, equalling the record for the earliest success set by United in 1907-08 and 2000-01 and replicated by Everton in 1984-85. "They've got a hell of an opportunity to go and do it now", Shearer added.
"Ederson has shown in his first season at the club that he has all the attributes needed to become one of the best goalkeepers in the world", he said.
In Guardiola, they have a manager who has won consecutive league titles at former clubs Barcelona and Bayern Munich.
It has been clear since the first few weeks of the season that Manchester City would regain the title this year.
City's 100-point haul comes after they set a new Premier League points record by beating Brighton in midweek, taking them past the total set by Chelsea in 2004/05.
The match looked nearly certain to finish 0-0 after a hard-working display by the Saints, until Kevin De Bruyne found Jesus in space and the striker sent a looping finish past Alex McCarthy to seal victory in the 93rd minute of play.