The Shih Tzu's owner, Shirley Braha, announced the tragic news Saturday on Instagram, writing ... "It is with much grief I share the news that Marnie passed away painlessly & peacefully in my home on Thursday afternoon at the age of 18."

She continued, "Her comfort had been notably declining over the past few days with little hope for improvement and she let me know she had had enough. She enjoyed her chicken until the very end." Braha goes on to thank everyone for embracing Marnie, explaining how her dog put her on the journey of a lifetime and how grateful she was for the love.

Braha ends her tribute post with a bit of info, and somewhat of a forewarning too ... saying Marnie will be buried at a pet cemetery in L.A., adding there'll hopefully be a public memorial for her whenever it's safe to hold one, in light of the coronavirus and all.

Marnie was adopted from an animal shelter in 2012 at the ripe age of 11 years old. Soon after, she went on to achieve viral fame because of her freakishly long (but super cute) tongue, which inexplicably hung out of her mouth at almost all times.

Marnie has posed with countless celebs over the years, including Jonah Hill, Tina Fey, Demi Lovato, James Franco, Betty White, Ed Sheeran, Katy Perry, Taylor Swift, Larry King, Aaron Paul, Usher, Selena Gomez, Lena Dunham, Riff Raff, Jason Schwartzman and more.

She once shot down an invitation to the "Wolrd Dog Awards" because, apparently, Marnie and co. felt she was too big for it. She might've been right -- Marnie got her own book deal at one point.

The doggo was 18 years old.