A post on Chyna's official Facebook page confirmed the entertainer, born Joanie Laurer, had died.
Chyna became a World Wrestling Entertainment star in the late 1990s and later appeared in both mainstream and pornographic films. She was also appeared on reality television shows, among them VH1's "Surreal Life" and "Celebrity Rehab with Dr. Drew."
The cause of death was not known.
Police in Southern California said they were responding to a 911 call from a friend of the former World Wrestling Entertainment wrestler when they found her dead in her Redondo Beach apartment.
A friend went to check on Chyna after she had failed to answer her phone for a few days, Redondo Beach police said in a statement. The friend told the 911 operator that Laurer wasn't breathing.
The 46-year-old was dead when officers arrived, police said.
Neither police nor coroner's officials have released any cause of death
An autopsy is planned in the next few days.
Laurer billed herself as the "9th Wonder of the World" because her wrestling predecessor Andre the Giant had already called himself the eighth.
She was a member of the wrestling squad that dubbed itself "D-Generation X," often wrestled against men and at one point was the WWE women's champion.
After leaving the WWE in 2001, Laurer posed for Playboy and appeared in adult films and on reality TV, including the shows "The Surreal Life" and "Celebrity Rehab with Dr. Drew."
A statement posted Wednesday night on her website read:
"Today we lost a true icon, a real life superhero. Joanie Laurer aka Chyna, the 9th Wonder of the World has passed away. She will live forever in the memories of her millions of fans and all of us that loved her."
Laurer was a native of Rochester, New York, and graduated from the University of Tampa in Florida before taking up wrestling.