"Last night we had to say goodbye to our dog Wolf," the television host, 62, wrote on social media, alongside a photograph of herself and wife Portia de Rossi posing with Wolf on their wedding day, back in 2008.
"He brought us so much love and joy. I hope we did the same for him," DeGeneres added of the beloved poodle-Maltese mix.
The couple, who are noted animal lovers, also shares dogs Kid, Augie, and Mrs. Wallis Browning, who they rescued last year, as well as three cats.
Wolf made his television debut in a throwback episode of The Ellen DeGeneres Show.
Bringing the young dog with her onstage, DeGeneres introduced her audience to Wolf, calling him the "cutest" in the world.
"I like him a lot," she added, urging the audience not to be too loud, as she wasn't sure how the young pup would handle all of the noise.