Stephens, the 2017 U.S. Open tennis champion, and Altidore, striker for the U.S. men's national soccer team and Toronto FC, said they are engaged after a three-year courtship, Sports Illustrated reported.
Both athletes posted photos and short messages on social media .
"Forever yes," Stephens posted on Instagram. "Forever starts now," Altidore wrote on his Instagram account.
Stephens, 26, is No. 8 in the WTA's world tennis rankings. She was the French Open runner-up in 2018 and played for the U.S. Fed Cup team that won the 2017 championship.
Altidore, 29, has scored 41 goals since he debuted for the U.S. national team in 2007, ESPN reported. He has played for Toronto FC in Major League soccer since 2015.