PSG needed only a point to be sure of becoming only the fourth Ligue 1 club to win three championships on the trot.
France international midfielder Blaise Matuidi put PSG on the road to glory after 17 minutes. The Argentine forward Ezequiel Lavezzi made it 2-0 eight minutes later.
Anthony Mounier halved the deficit just before half-time. But Laurent Blanc's men held on for their eighth consecutive victory.
"For various reasons we didn't start the season well. But we knuckled down to some hard work and I kept my faith in the squad," said Blanc. "I did well because they've repaid that trust. I've also got to thank the backroom staff. They do a lot of hard work which isn't obvious. I've done well to get them and without them we wouldn't have this success."
It's Blanc's second title with PSG and his third as a coach in Ligue 1. The 49-year-old former France international was at the helm when Bordeaux won the championship in 2009.
It was experience of a French title run-in that gave Blanc the edge over Hubert Fournier and Marcelo Bielsa, his counterparts at Lyon and Marseille respectively.
"I said after the 30th round of games that the champions would emerge from the team that kept its nerve and won matches," he said. "I said back then that I hoped it would be us. And it has been us."
The unbeaten run took PSG from second behind Lyon to champions with a game to spare.
Lyon by contrast have slumped over the same period taking 14 out of a possible 24 points. Their 1-1 draw against Bordeaux at the Stade Gerland assured them of second place and automatic qualification for the group stages of next season's Uefa Champions League.
Fournier said on Saturday night that he was pleased with the season.
"When you think that at the end of August we were in 17th place, we've done a lot of work to get to this point. Even if we've dropped off recently, it's important to look at the season as a whole."
It will be intriguing to see whether Bielsa will offer such sober analysis at the end of the season.
When Marseille hosted PSG on 5 April at the Velodrome they, Lyon and PSG were separated by two points in the tug for the title.
The 3-2 defeat to PSG was followed by losses at Nantes and Bordeaux and a humiliating 5-3 capitulation at home to Lorient.
The decline was arrested with victory over Metz but they'd lost the plot as far as the title was concerned.
Marseille thrashed Lille 4-0 on Saturday night and are in the reckoning for third place, which leads to the qualifying rounds for next season's Champions League.
Monaco currently occupy the berth and will secure it with victory at Lorient on 23 May. Should they only take a point from the game, Marseille, who have a better goal difference, will claim third if they beat mid-table Bastia at the Velodrome next Saturday evening.
Fifth-placed Saint Etienne are also in with a chance of third place. They'll have to beat Guingamp convincingly and hope that both Monaco and Marseille fail to take maximum points in their final games.
While the last Champions League spot is yet to be resolved, at the other end of Ligue 1, Evian trickled away to Ligue 2 after losing 2-0 to St Etienne.
Evian join Metz and Lens in the journey to second tier. And it's a second division side that stands in the way of PSG's quest for an unprecedented treble.
Auxerre will take on PSG in the final of the Coupe de France on 30 May at the Stade de France.
PSG pocketed the Coupe de la Ligue last month after hammering Bastia 4-0. Only three teams beat them in the top flight during their latest title-winning season.
After the millions QSI have spent on the side over the past three years, a mid-table outfit from Burgundy will start the final as overwhelming underdogs.