Two glorious early goals from league player of the season Phil Foden created a party atmosphere in the sunshine at the Etihad Stadium, before a stunning bicycle kick from West Ham's Mohammed Kudus before halftime briefly unnerved the hosts.
But victory never looked in doubt and Rodri sealed the points with a low shot just before the hour from outside the area, giving Pep Guardiola's side a sixth title in seven years.
City now have the chance of winning the double when they face Manchester United in the FA Cup final next Saturday.
Fans danced in their seats, belting out "Champions again!" and "Are you watching Arsenal?" before pouring onto the pitch and setting off blue flares when the final whistle sounded.
In one of the closest title races in Premier League history, Mikel Arteta's Arsenal chased them valiantly and could have taken the championship had City dropped points.
But the Londoners' 2-1 win in their home game against Everton was in vain, leaving them two points behind.
BRILLIANT FODEN
Foden's already brilliant season got even better when he arrowed the ball into the top corner in the second minute then capped a fine team move to sweep home the second in the 18th.
"It's so hard to put into words what we've done today," he said. "No team has ever done it. You see what it means to the fans and it means to us. Working all year for this moment.
"I thought today we just looked confident and just played our football and in the end it paid off."
The midfielder has scored 19 league goals this season and has won six Premier League titles at just 23, making him one of England's best hopes for this year's Euros in Germany.
At the final whistle, blue-clad fans defied stewards to rush onto the pitch. The players hugged each other and, once again, later danced in triumph together in their dressing room.
"Blue Moon," the club anthem, boomed around the ground.
City's latest title was won with 91 points, to Arsenal's 89.
On Sunday, they even had the luxury of seeing 27-goal league Golden Boot winner Erling Haaland fluff two close-range chances.
"It's not bad," Haaland said modestly of his second successive Premier League Golden Boot in two seasons with City. "There's not much to say, it's better to just play football and don't speak too much. Let other people do the speaking."
The result left West Ham ninth following a disappointing end to the season at the end of David Moyes' reign as manager.
FINAL FLOURISH
After trailing Liverpool and Arsenal for large periods of the season, City came good in the run-in - as is their custom - winning nine league matches in a row and going unbeaten in 23.
"It's a very, very tough league to win," said City captain Kyle Walker. "I looked at the Italian league, German league, Spanish league, the winners are 10-15 points clear. Fair play to Arsenal and Liverpool for what they have done throughout the season, making sure they push us right to the limit."
City's latest Premier League title followed a crushing Champions League quarter-final defeat on penalties by their Spanish rivals Real Madrid. Last year, City won the treble of Champions League, FA Cup and Premier League.
In a reminder of tougher times in the past, former City forward Paul Dickov presented the trophy on Sunday - 25 years after a famous playoff win over Gillingham dragged the team out of the third tier of English football.
Guardiola donned a City top, waving to fans and high-fiving staff, as the Spaniard received his medal, followed by the players who lapped up the fans' adoration one-by-one before embarking on a lap of honour.
Guardiola is the fourth manager to win six or more top-flight titles in the 136-year-old English league, along with record holder Alex Ferguson with Manchester United (13), Aston Villa's George Ramsay and Liverpool's Bob Paisley (both six).
"It feels as amazing as the first one (title)," said Belgian midfielder Kevin De Bruyne, who came back from injury to drive City's final push.
"We worked so hard for it. It's been a top battle with Arsenal and Liverpool this year. To again be doing something historic is amazing."
"This is one of my most special. I had a tough year, to be out for six months, but to come back."
Despite the deserved plaudits earned by City, for many fans of other clubs their dominance is tarnished by Premier League charges over alleged breaches of financial rules during the ownership of billionaire Sheikh Mansour bin Zayed Al Nahyan.
City deny any wrongdoing and are contesting the charges.
Fellow Premier League sides Everton and Nottingham Forest were both deducted points this season after admitting charges. It is unclear when Manchester City's case will conclude.
