The Qatari-owned club needed only a point but ended the night eight points clear of their closest rivals Olympique Lyonnais who were held to a 1-1 home draw by Girondins Bordeaux.
The title kept Laurent Blanc’s side on course for a sweep of domestic honours, with the Parisians already winners of the League Cup and facing second tier AJ Auxerre in the French Cup final at the end of the month.
Monaco stayed third on 68 points, four adrift of Lyon, after beating Metz 2-0 in the principality while Olympique Marseille and St Etienne also won to stay tied on 66 in the battle for a place in next season’s Champions League preliminary round.
Evian Thonon Gaillard joined Racing Lens and Metz in being relegated after losing 2-1 to St Etienne.
“I love watching the scenes of joy, whether on the field or in the locker room,” said a delighted Blanc. “The players on the field earn the titles, we play a small part.
“We must let the players express themselves and the coach must always be behind them. It’s not up to him to be at the front of the stage.”
Midfielder Blaise Matuidi put PSG ahead in the 17th minute, slotting past goalkeeper Jonathan Ligali after a defence-splitting pass from Adrien Rabiot.
Ezequiel Lavezzi made it 2-0 in the 25th minute, from a cross by Serge Aurier, his eighth league goal of the season but Montpellier pulled one back five minutes before the break through Anthony Mounier’s shot into the top corner.
The win was the eighth in a row in the league for PSG who claimed their fifth French title.
The match, watched by a 27,930 crowd at the Stade de la Mosson, ended with flares lit in the stands and thrown on to the edge of the pitch with stewards stamping out the flames.
“I still enjoy doing this job,” said Blanc. “I have to thank my staff because without his staff a coach is nothing at all.”
(Reporting by Alan Baldwin in London, editing by Tony Jimenez)