Josie Harris -- who has 3 children with Floyd Mayweather -- was found dead at her home in Valencia, CA on Monday night ... TMZ Sports has confirmed.
Law enforcement sources tell us ... officials were called to the home around 9:30 PM and when they arrived, they found 40-year-old Harris unresponsive in her car.
She was pronounced dead at the scene. We're told there does not appear to be any foul play and the case is being treated as a death investigation as opposed to a homicide probe.
Josie had a tumultuous relationship with Mayweather.