Sofia Kenin played the "five best shots of my life" to become the newest young champion of women's tennis.
Kenin is the youngest winner of the title since Maria Sharapova in 2008 and follows in the footsteps of Naomi Osaka, Ashleigh Barty and Bianca Andreescu, who have all won their first slam finals in brilliant fashion over the past 18 months.
She appeared on the verge of tears at various points during the deciding set, dropping her racket and covering her hands with her face in disbelief when Muguruza's second serve landed long on match point.
"These past two weeks, there have been a lot of emotions," she said later. "You guys could see after the match how much it all meant to me.
"This is such an honour. I'm so proud of myself, my dad, my team, everyone that has been around me. We've all worked hard. We've been through tough times. We did it. We fought. I'm just on cloud nine."
A child prodigy who had remained surprisingly under the radar despite beating Serena Williams at the French Open last year, Kenin has quickly built a reputation for intelligence and feistiness.
She appeared to relish being booed by the crowd during that victory over Williams in Paris, and greeted the biggest pressure moments in this match as if she was insulted by them.
The five points she played to hold serve from 0-40 at 2-2 in the deciding set were not just the key to the match but a demonstration of a very special talent and mentality.
"That's the game I feel like changed things," said Kenin. "I had to play my best tennis. I did. After that, I was on fire. I was ready to take the beautiful trophy.
"I knew I had to take my chance. I had to be brave playing a two-time grand-slam champion. All respect to her. She played a really tough match. Every point, it was such a battle. A lot of moving. A lot of emotions on court from both sides.
"I knew I needed to come up with the five best shots of my life. That game is going to be with me forever."
Kenin's gifts were evident as soon as she picked up a racket aged three. Her father Alex, a recreational player back in his native Russia, has coached his daughter ever since, and the pair have always imagined this moment.
"I really have him to thank," said Kenin, who will climb to seventh in the world rankings, overtaking Serena Williams as the American number one.
"We've been dreaming about this. It's a dream come true for us. He's told me a lot of positive things. He knows exactly what he's talking about. He's helping me with the game plan. He sees everything well. Even though I don't like to admit it sometimes, to tell him he's right.
"He really works hard. Just thank you to him. We can share this forever."
Kenin's mother Svetlana remained back home in Florida and did not know her daughter had won her first grand-slam title until a phone call after the match.
"I called her right after just to tell her that everything's fine, I won, she can just relax now," Kenin said.
"My mom cannot watch me. Even when she knows the results that I won, she still won't watch. I can see she's still nervous."
Muguruza had been hoping to win her third slam title having emerged from the wilderness under the guidance again of Conchita Martinez, with whom she lifted the Wimbledon trophy in 2017.
Muguruza was tearful at the end but was able to reflect on a tournament that has shown her the way back to the top of the game.
The 26-year-old said: "I'm not very happy about my performance. I think I had to play better today because she came up with a great level. At the important moments I didn't find my shots. I think she found her shots.
"I did feel a little bit of a lack of energy after so many matches. Physically it was a tough battle out there. Right now it's tough to be happy, although it has been an incredible tournament.
"You lose a final, but you've got to make it to the final to be able to win or lose. I think she played very well.
"I think I'm in a good process. I think I felt my game much better than before. I think I've got to keep it that way, keep working physically. These events are really long, so you've got to be strong."