Michael Keaton is mourning the loss of his “true friend” and “Beetlejuice” co-star Catherine O’Hara.

“We go back before the first ‘Beetlejuice,’” Keaton reflected via Instagram Friday as he shared a recent photo of the pair.

“She’s been my pretend wife, my pretend nemesis and my real life, true friend. This one hurts. Man am I gonna miss her. Thinking about [Bo] as well,” he concluded in his touching tribute, referring to O’Hara’s husband of 33 years, Bo Welch.

O’Hara and Keaton both starred in Tim Burton’s 1988 cult classic, playing Delia Deetz and the title character, respectively.

The dark comedy became so beloved, it ended up having several Broadway runs from 2019 to early 2026 — where O’Hara was once honored by the musical cast.

The duo went on to collaborate on several other film projects including “The Paper” in 1994 and “Game 6” in 2005, where they played husband and wife.

Most recently, Keaton, 74, and O’Hara reunited for the long awaited “Beetlejuice” sequel in 2024.

In January of that year, the “Schitt’s Creek” star gushed over being able to work alongside Keaton in “Beetlejuice Beetlejuice.”

“I had a little two-person moment with Michael as Beetlejuice. I’d been in the first movie in group scenes with Michael, but in this, I had an actual moment where the two of us just,” she told People.

“And it was just so crazy and thrilling, really to just be face-to-face with Beetlejuice. He looks the same. Beetlejuice has aged very well.”

The following month, Keaton told the outlet how much care he and O’Hara put into the sequel to make sure it was done “right.”

“We thought, ‘You got to get this right. Otherwise, just don’t do it. Let’s just go on with our lives and do other things,’” he explained.

“So I was hesitant and cautious, and he was probably equally as hesitant and cautious over all these years,” Keaton continued. “Once we arrived, I said, ‘OK, let’s just go for it. Let’s just see if we can do it, if we can pull this off.”

O’Hara died on Friday after suffering a “brief illness,” CAA told Page Six in a statement.

The cause of death of the “Home Alone” star — who had a rare medical condition called dextrocardia — has not been revealed.

She was rushed to a Los Angeles hospital early in the morning on Friday in “serious” condition and subsequently died, a Los Angeles Fire Department spokesperson told us.

O’Hara’s was last publicly seen in September 2025 at Apple TV+’s Primetime Emmy Party in Los Angeles celebrating her show with Seth Rogen, “The Studio.”

“Really don’t know what to say… I told O’Hara when I first met her I thought she was the funniest person I’d ever had the pleasure of watching on screen,” Rogen captioned an Instagram Friday.

“‘Home Alone’ was the movie that made me want to make movies. Getting to work with her was a true honor. She was hysterical, kind, intuitive, generous… she made me want to make our show good enough to be worthy of her presence in it. This is just devastating. We’re all lucky we got to live in a world with her in it,” he wrote.