Chloe Kim defeated fellow American Kelly Clark to win the Women's Snowboard SuperPipe competition on Saturday in Aspen.
Kim, 14, today posted a photo of her on top of the podium, saying "it was one crazy night!"
Kim has been snowboarding since she was 4 years old, according to the U.S. Ski and Snowboard Association.
"I am just so amazed that I was able to land all that. It was so fun," Kim told ESPN after she won.
Kim had a mark and bandage on her face because she crashed in practice before the competition, according to one of her coaches, Benjamin Wisner, whom she trains with in Mammoth, California.
While Wisner didn't work with Kim in the weeks leading up to the X Games, he "thought she had a chance, for sure," he told ABC News today.
"The run she's been working on is very technical," said Wisner. "She had good style."
Wisner has been training Kim in Mammoth for about five seasons.
If she was nervous before the competition, Kim didn't show it. "So ready for tomorrow!" she wrote on Instagram. "Lets do this thing!"
"I'd say the nerves were there, but she thrives in that situation," Wisner said. "I think every athlete gets nervous. But Chloe has a great attitude and a pretty strong mental game. She's a great competitor. She can relax even in nervous situations. I'm sure there was some nerves, but she just loves to snowboard and she loves riding in front of a crowd."
Wisner texted Kim on Saturday night after her win, he said, telling her he was proud of her.
"She said, 'thanks,' and that she's really proud of herself," Wisner recalled.
X Games Vice President Tim Reed was also impressed, saying in a statement, "Chloe showed tremendous resiliency after a hard fall in practice, coming back with the focus and determination to put down a gold medal run and becoming the youngest gold medalist in X Games winter event history. Quite an accomplishment for a 14-year-old - and anyone for that matter."
Kim wasn't the only record breaker at Saturday's X Games. According to ESPN, day four of this year's competition broke a record for winter crowds, with 48,500 spectators in attendance.