But Monaco are the champions and proved in their Ligue 1 opener they will provide a formidable challenge
PSG will expect 222-million-euro man Neymar to fire them not just to domestic glory but also European success following his sensational move from Barcelona.
But Monaco are the champions and proved in their Ligue 1 opener they will provide a formidable challenge to the mega-rich Parisians with goals from Brazilian Jemerson, Colombia's Radamel Falcao and Kamil Glik of Poland allowing them to twice come from behind and snatch three points.
Toulouse threatened to spoil the party by twice taking a shock lead, the first on six minutes.
In what looked like a set corner routine that didn't quite go to plan, Andy Delort had to back track out of the area to chest the ball into the danger zone, where the unmarked Zinedine Machach had time to swivel and rifle a volley across Danijel Subasic.
Monaco may have been forced into selling several stars over the summer transfer window, with Benjamin Mendy, Tiemoue Bakayoko and Bernardo Silva moved on to pastures new, but they were not the top Ligue 1 goalscorers with almost three goals a game last season for nothing.
Soon enough, the hosts were turning the screw as Thomas Lemar had a shot blocked on the edge of the area before Kylian Mbappe -- the Real Madrid target who could fetch a sum close to Neymar's -- was denied from a tight angle by goalkeeper Alban Lafont.
Mbappe should have been celebrating his first goal of the season on 19 minutes but Kelvin Amian got back to to intercept a Falcao cross and deny the teenage starlet a tap-in.
The inevitable came on 28 minutes, though, and in simple fashion as centre-back Jemerson headed home a near post corner from Joao Moutinho, as Toulouse's defence stood ball-watching.
Monaco captain Falcao had been in the thick of things, although his sights were off as he headed one chance over, saw a left-foot shot blocked and fired a free-kick wildly into the stands.
Monaco carried on after half-time with Lemar forcing Lamont into a plunging save from a well-struck free-kick.
But there was another sting in the tail as reported Chelsea target Djibril Sidibe gave the ball away cheaply to Jimmy Durmaz, who slipped the ball inside to Delort to turn and fire home a daisy-cutter inside Subasic's right-hand post.
Eight minutes into the second period and Monaco had it all to do again.
But they didn't have long to wait as Falcao got the goal his industry, if not accuracy, deserved on 58 minutes, holding off Francois Moubandje to power home Jorge's deflected cross.
Mbappe was a constant menace down the left but his final ball often left much to be desired, while Amian ensured with one crunching challenge that the teenage starlet would not be allowed an easy ride.
But while Toulouse defended staunchly for the most part, their command of the skies was distinctly lacking and a third headed goal gave Monaco the lead as centre-half Glik got the slightest flick of a hair on Mountinho's chipped free-kick to flummox Lamont.
Substitute Guido Carrillo could have sealed the win in stoppage time from fellow replacement Allan Saint-Maximin's cross but Lafont stood up well to block the Argentine's shot.