‘The most iconic baby at the US Open’ goes viral for getting autographs of the biggest names in tennis

She was having a ball.

A 9-month-old became “the most iconic baby at the US Open” for getting the biggest names in tennis to autograph her helmet.

Baby Stella Wagley of Grand Rapids, MI, went to the Queens tournament for the first time on Aug. 28 and 29 — and the compilation video of her getting the John Hancocks of 11 stars like Coco Gauff, Carlos Alcaraz, Aryna Sabalenka, Jannik Sinner and John McEnroe went viral, racking up 2.5 million views.

“My favorite part about it was seeing everyone’s absolute genuine reaction. Nobody knew they were going to see a baby in a helmet,” Stella’s mom, Katerina Buck, told The Post.

Buck explained that Stella had just started wearing the cranial remolding helmet in order to assist in redirecting the growth in certain spots of her head.

The helmet signing started with Alcaraz, ranked No. 2 in the world, when Buck’s sister, Eleni Sabracos, brought Stella down to the stands closest to the court, where children gathered to get his signature.

Buck recalled that Eleni started “inching closer and closer” to him while holding Stella.

“And all the sudden he stops … You could see him do the triple take, like, ‘Wait, that was a baby.'”

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The most memorable signing was from tennis legend McEnroe, who grew up in Queens and won the US Open four times.

“That one was hilarious because he’s like, ‘What? I think I’m going to break her neck,'” she recalled.

The sweetest autograph she got was from Sinner, ranked No.1 in the world, who is Brooks Nader.

“He was so cute, he grabbed Stella’s hand while he was signing it,” she gushed.

“My cousin texted me after, when she saw his reaction. She was like, ‘Oh my gosh. That guy is gonna be such a good dad.'”

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Taylor Townsend, ranked No. 1 in doubles, was the nicest, she said.

“She said, ‘Well, how can I say no to that one?'”

But her favorite autograph came from Karolína Muchová.

“She did the ‘aww’ face. She’s my favorite women’s player, so to get that reaction killed me.”

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Buck said the video helped raise awareness for the helmet, which Stella may need to wear for up to six months.

“You get so many people who are like, ‘What is wrong? Why does she have the helmet?'” she said.

“My mom works in this building that has a lot of great nonprofits and she had a Special Olympics employee chase her down yesterday to tell her how much they appreciate what her daughter did to bring awareness to something that so many people feel and experience.”

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The Instagram video, which Sabracos posted on Aug. 31, got more than 400 comments from new fans of Stella.

“That helmet’s gonna be worth a fortune in the future,” one said, while another added, “That should pay for college.”

“Everyone’s laughing at me, but I would never [sell] that,” Buck said.