The 37-year-old actress - who married the talk show host at their Beverly Hills home in August 2008 - had her request to officially become Mrs. DeGeneres granted by a judge yesterday (23.09.10).
Portia said in a statement: "I am thrilled to legally adopt my wife's name. I will continue to use Portia de Rossi for professional purposes."
The former 'Arrested Development' star initially signed documents requesting to take her spouse's name in March, before officially filing a petition in a Los Angeles court in August.
Although the couple have now further cemented their six-year relationship, Ellen, 52, recently admitted she and Portia have no plans to start a family.
She explained: "I don't think we're going to have kids. We have animals, and we love them. And, you know, we are Brand New aunts. Her brother and his wife just had a baby girl who's a month old now, and it's fun to be a part of that.
"It's just a huge responsibility, and I don't know if that's something we want to take on. We're very happily married without children."