The 'American Idol' host - who is dating 'Rock of Ages' star Julianne Hough - is thought to have paid within a few million dollars of the massive asking price with the deal agreed and set to close this week, according to gossip website TMZ.com.
Ellen - who spent one season on the judging panel of 'American Idol' - and Portia have sold the property at a loss after spending $48 million assembling the huge estate.
They bought the $30 million 9,500-square-foot single-story house and spent millions more on the surrounding properties, before beginning extensive renovation work.
The home sits on 2.87 acres just off Coldwater Canyon - near the Santa Monica Mountains - behind gates on its own street and also includes two guesthouses totaling 15,000 square feet, a three bedroom house, and according to official listings "every conceivable amenity and state-of the-art security".
Portia previously revealed the pair fell in love with the property - which previously belonged at different times to Laurence Harvey, Joan Collins and 'Will & Grace' co-creator Max Mutchnick - when they went to watch a screening of Ryan's show 'American Idol'.
She told Architectural Digest: "We'd heard how beautiful it was and then we came over to watch 'American Idol'. We pulled into the driveway and we just knew before we even walked through the gate."