Singer Joshua Radin, who sang at the couple's wedding, also sent DeGeneres and de Rossi a special anniversary message, which DeGeneres reposted.
"Nine years ago today, these two incredible women got married and asked me to sing some of my songs to them while they were celebrating their most special day," Radin wrote. "It's still one of the most fun things I've ever done. Happy anniversary @theellenshow and @portiaderossi."
Earlier this month, DeGeneres gushed about de Rossi in an interview with Good Housekeeping.
"Portia understands me completely," she expressed. "In our vows, she recited a quote, ‘It is good to be loved. It is profound to be understood’ -- and to me, that’s everything. What ‘I love you’ really means is ‘I understand you,’ and she loves me for everything that I am. She supports me and makes me happy.”