A Los Angeles Superior Court commissioner granted De Rossi's request to take the last name of her partner during a closed hearing Thursday. The television star will now legally be known as Portia Lee James DeGeneres.
The couple was married in August 2008. The 37-year-old Australian-born actress asked for the name change last month.
Neither woman attended the hearing. They married during the five-month window in which gay marriage was legal in California.
Portia DeGeneres is well-known for her roles on several television series, including "Ally McBeal," "Arrested Development" and "Better Off Ted."