Zagitova received 82.92 points, thus breaking the world record of another Russian athlete Evgenia Medvedeva. Medvedeva skated her short program and Zagitova performed her free skate to help Team OAR to silver.
Medvedeva most recently lost to her 15-year-old training mate Zagitova at the European Championships in Moscow in January, setting up a tight race in PyeongChang. Kaetlyn Osmond of Canada won the bronze medal, but the real battle was between the two Russians, who are friends off the ice and share the same coach.
The free skate program is set for Thursday. Nagasu was ninth, with Chen 10th and Tennell 11th.
Four-time national champion Miyahara delivered a personal-best free skate (146.44 points) to finish with a total score of 222.38, while Japan's Kaori Sakamoto was sixth with 209.71.
Some of Russia's top athletes were not cleared to compete by the International Olympic Committee (IOC). "I think this is only the beginning".
Zagitova, the world junior champion last season, cleanly landed a triple lutz/triple loop combination jump, followed by a triple flip and a double axel.
"When we take the ice, this is sport and we must fight", said Medvedeva, who certainly sounds, of the two, like she's applied Sun Tzu's The Art of War to figure skating. She pulled up several places after a strong free skate to "Clair de Lune". A fall on the back end of a combination jump - Tennell had been virtually ideal with her jumps in her breakthrough season - was costly.
The once-vaunted US skating program hasn't had a medalist since Sasha Cohen took silver 12 years ago in Turin.
Two of the country's most recognizable skaters did not even make the team for the Pyeongchang Olympics; Wagner finished fourth at the US championships and was not chosen, and Gracie Gold did not compete this season.
Neither Zagitova nor Medvedeva fell on the ice.
Osmond is a terrific short program skater and her Black Swan long program is exquisite.
"I won. Honestly, my hands are shaking, because I haven't understood yet that I am an Olympic champion", said Zagitova, who recovered nicely from a blip on her first planned combination jump at Gangneung Ice Arena.
The trio US women are well off the pace and need a big rally in their free skates to avoid the worst showing by the American contingent in Olympic history.
No U.S. woman has had sustained worldwide success since five-time world champion Michelle Kwan's run from the mid-1990s through the mid-2000s. "It was not my best, but it was OK", she said.
"I very rarely make a mistake", she said.
Italy's Carolina Kostner, the 2014 Olympic bronze medalist, is already the grand old lady of figure skating-at 31.
No one expected Tennell, Nagasu and Chen to experience falls during the short program, but that's the reality the United States is dealing with halfway through the women's competition.
"I know that it would mean a lot to him to be back here, a part of him is in South Korea always", says Vonn, who shared her story with The Associated Press and the Chosun Ilbo newspaper. The U.S. Figure Skating Association banned her for life after her motley crew of hangers-on bashed Nancy Kerrigan's knee in 1994, launching one of the most freakish sports stories ever.