DeGeneres says that with the passage of California's Proposition 8, "we took a giant step away."
DeGeneres wed actress Portia (POR'-shuh) de Rossi in August, following a May Supreme Court decision legalizing same-sex marriage in California.
She contributed $100,000 to fight the amendment on Tuesday's ballot.
DeGeneres asserts she will "continue to speak out for equality for all of us."