Rosie O'Donnell Saved Estranged Wife Michelle Rounds' Life

Rosie O'Donnell saved the life of her estranged wife by keeping her on the phone while EMTs rushed to help her ... TMZ has learned.

Sources familiar with the situation tell us ... Michelle Rounds had overdosed on pills after threatening to end her life. We're told Rosie got wind of Michelle's plan, called her and tried talking her out of it. Rosie got someone to call 911 as she stayed on the phone with Michelle.

Law enforcement confirms that Michelle was rushed to a local Nyack, NY hospital from a hotel at 11:15 PM Tuesday.

As one source put it ... Michelle wouldn't be alive today without Rosie's intervention.

We're also told the trigger for Michelle was child custody. Sources tell us Michelle lost custody of their 2-year-old daughter to Rosie, and that sent her over the edge.

Rosie even comforted Michelle while in the hospital.

Calls to Rosie's rep were not returned.