As part of the deal, Stewart will serve as a brand ambassador on and off the court, and she'll receive her own signature shoe.
"I am proud to join the Puma family," Stewart said in a press release. "We share a vision to grow the sport and welcome everyone - specifically women and girls - globally.
"The genuine investment Puma has shown to collaborate with and activate around women, including the commitment to a signature performance shoe, is something that I hope serves to raise the expectations and standards of the generations of basketball players who follow me."
Stewart, who spent the last five years as a Nike athlete, is the 10th WNBA player to receive a signature shoe, and the first over the last decade. She'll get control over the design, colors, and messaging of her shoe, and Stewart wants men and boys to wear it as well, according to Mirin Fader of The Ringer.
"Where others saw a risk, Puma took advantage of it," Stewart told Fader. "Women's basketball players deserve to have signature shoes.
"We're going to be helping move the needle forward for women in sports and women's basketball."