Simone Biles, 4-time Rio gold medalist, signs with Mattress Firm

Simone Biles, the American gymnast who won a record four gold medals at the Olympics in Rio, has signed her first post-Games endorsement deal.

Biles, 19, has agreed to a multiyear deal with Mattress Firm, the largest mattress retailer in the United States.

Financial terms were not disclosed.

Ken Murphy, CEO of Mattress Firm, said the deal was good for the company, which did $2.5 billion in sales in 2015, and good for Biles.

"We think she and her team deserves every penny she can get," Murphy said.

While Biles said she didn't have any particular sponsorships in mind after her performance in Rio, where she won gold medals in the individual all-around, vault and floor exercise, and a team gold medal, she said any deal she signed would have to make sense.

"My endorsements have been very well planned out," Biles said. "Each of them mean something to me in terms of how it can make me better. It's very important for me to get a good night's sleep so I can deal with the day."

While the company has more than 3,500 stores in 49 states, Murphy said the Mattress Firm will use Biles in Houston, where the company is headquartered and where Biles has lived since she was 3 years old.

Murphy said Biles is the perfect spokesperson for the company's program of supporting foster homes. Biles was in and out of foster facilities as a child before she was taken in and raised by her grandfather and his second wife.

"The entire nation watched in awe as she became our most decorated Olympian gymnast," Murphy said. "We're thrilled to be able to use Simone to springboard what we're doing for this country in bringing national awareness to the foster care system and this company."

"I know what it's like to only have the clothes that are in your pack," Biles said. "I want other foster kids to know that they are not alone and they can feel like they can do anything."

Biles is expected to benefit from the fact that many Olympic stars are still amateurs in college -- including swimmers Katie Ledecky, Simone Manuel, Ryan Murphy and Lilly King -- and can't do endorsement deals.

Mattress Firm joins P&G, Nike, Hershey's, United Airlines, GK Elite and Core Power on Biles' growing endorsement roster.