A Norwegian racer was in third position, though it wasn't Henrik Kristoffersen, who has been Hirscher's main rival this season in the World Cup.
Instead it was Leif Kristian Nestvold-Haugen, who had 0.66 to make up in the second run later in the afternoon. Nestvold-Haugen took bronze in giant slalom at the 2017 world championships, which Hirscher won.
"He's been on a different level all year," Nestvold-Haugen said of Hirscher's run. "He's in good balance. He skis clean. Good tactics."
Kristoffersen, a three-time runner-up behind Hirscher in World Cup giant slaloms this season, was 1.31 back in 10th place.
Erik Read is the top Canadian after the first run in 16th place. Canada's Trevor Philip is 24th, Philip Brown 25th and James Crawford 31st.
Defending champ struggling
Defending champion Ted Ligety is struggling in his bid to defend the title he won at the 2014 Sochi Olympics.
Ligety was out of the top 15, trailing 2.44 behind Hirscher's target of 1 minute, 8.27 seconds, and said he skied himself out of medal contention being too cautious.
"If something funky happens, then maybe I have a hope and a prayer," Ligety said. "But if it's a normal, fair race, then this is way too big of a detriment to climb out of."
The event started under blue skies on a clear, cold day at Yongpyong Alpine Center.
Despite that, two top racers had crashing falls though the finish line. Both Luca de Aliprandini of Italy and Manuel Feller of Austria lost balance approaching the next-to-last gate and were disqualified. De Aliprandini had been running with the second-fastest time.
Other racers to take tumbling falls included the only Russian in a 110-man lineup, Ivan Kuznetsov, and the highest-ranked South Korean, Jung Dong-hyun.
North Koreans Choe Myong Gwang and Kang Song Il were scheduled to start later, wearing bib Nos. 109 and 110.