Coming around a left-turn gate, she lost control, slid and fell on her side.
The 26-year-old Shiffrin was trying to become the first Alpine ski racer from the United States to win three Olympic golds across a career.
She arrived in China as one of the most-watched athletes in any sport at the Winter Olympics, a superstar who has dominated ski racing for long stretches in recent years. She has said she hoped to enter all five individual events at Yanqing Alpine Skiing Center.
Her next race is the slalom on Wednesday. Shiffrin won that at age 18 at the 2014 Sochi Games.
Shiffrin has spoken openly about the pressure created by the weight of expectations — her own, of course, and those of fans, but also coaches, friends and family. She also is up-front about the burden of dealing with the accidental death of her father, Jeff, two years ago.
Her debut in Beijing was over quickly. She slipped and tried to right herself, but it was too late.
Eventually, Shiffrin got up and stopped on the side of the hill at the course known as The Ice River, stuck her poles in the snow and put her hands on her hips.