The Frenchman, bidding for a seventh FIA World Rally Championship crown, was fastest in the tricky and technical 4.33km Sottozero The Monza Legacy in a Toyota Yaris by 0.5sec from Thierry Neuville.
The four drivers fighting for the title filled the top four places. Reigning champion Ott Tänak was 1.5sec behind Hyundai i20 team-mate Neuville, with championship favourite Elfyn Evans fourth, a further 0.7sec back in another Yaris.
A mix of fast smooth asphalt on the circuit itself and twisty narrow tracks in the interior made a stage of contrasts. The morning’s fog had lifted but conditions were still slippery in temperatures of only 3°C.
Video: ACI Rally Monza SS1
Ogier, who started 14 points behind Evans, has a simple master plan. “I need to win, so I need to give everything. The conditions will still play a big part so we have to be good,” he said.
After spinning in shakedown this morning, Evans was again ragged. The Welshman almost overshot a junction after sliding wide at a chicane and admitted: “I was a bit careful and we’re going to have to go quicker than that during the weekend. It was key to get through this one.”
The third Yaris of Kalle Rovanperä and Esapekka Lappi’s Ford Fiesta filled the top six, although Finn Lappi almost misjudged his braking at the final corner. Dani Sordo, Gus Greensmith, WRC 3 leader Jari Huttunen and Teemu Suninen completed the top 10.
It was a disastrous start for Takamoto Katsuta who overshot a corner and, in trying to rejoin the stage, crashed into a wall just 2.3km after the start. The impact damaged the steering on his Toyota Yaris and the Japanese pilot went no further.
In WRC 2, Mads Østberg was 1.3sec faster than title rival Pontus Tidemand, while Huttunen stopped the clocks 0.7sec up on Andreas Mikkelsen in WRC 3.
The rally continues on Friday with a full day of Monza action. Two morning passes through Scorpion (13.43km) are followed by a double run over Cinturato (16.22km). The leg closes with PZero Grand Prix (10.31km) in darkness, taking the day’s tally to 69.61km.
Full coverage from ACI Rally Monza is available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.