Nancy Meyers shared an emotional tribute to Diane Keaton, reflecting on their decades of collaboration and close friendship.

The filmmaker wrote some of Keaton’s most beloved films, including 1987’s “Baby Boom,” 1991’s “Father of the Bride,” and 1995’s “Father of the Bride Part II.” Meyers later wrote and directed 2003’s “Something’s Gotta Give,” which Keaton starred in with fellow acting great Jack Nicholson.

“We have lost a giant,” Meyers, 75, wrote on Instagram Monday. “A brilliant actress who time and again laid herself bare to tell our stories.”

“As a woman, I lost a friend of almost 40 years — at times over those years, she felt like a sister because we shared so many truly memorable experiences,” she continued. “As a filmmaker, I’ve lost a connection with an actress that one can only dream of.”

Meyers noted how she and Keaton truly understood each other and praised the Oscar-winning actress’ humor and vulnerability.

“She goes deep,” Meyers shared. “And I know those who have worked with her know what I know… she made everything better. Every set up, every day, in every movie, I watched her give it her all.”

Meyers concluded, “She was fearless, she was like nobody ever, she was born to be a movie star, her laugh could make your day and for me, knowing her and working with her — changed my life. Thank you Di. I’ll miss you forever.”

Keaton died on Saturday in California. She was 79-years-old.

Though her cause of death is still unknown, her friend told People that the actress’ health had rapidly declined unexpectedly in past few months.

“In her final months, she was surrounded only by her closest family, who chose to keep things very private,” the source said. “Even longtime friends weren’t fully aware of what was happening.”

Keaton is survived by her two children — daughter Dexter, 29, and son Duke, 25 — whom she adopted in her ’50s.

Though she never married, her famous exes are reportedly taking her death hard.

Woody Allen — whom Keaton dated for a few years, starting in 1969 — penned an emotional tribute to the actress, writing, “A few days ago the world was a place that included Diane Keaton. Now it’s a world that does not. Hence, it’s a drearier world.”

Al Pacino, whom Keaton was in an on-again, off-again relationship with from 1974-1990, now regrets never marrying her, a friend of the actor told the Daily Mail.

“I know he will forever regret he didn’t make his move when he had the chance,” the source said. “For years after he and Diane split, Al used to say, ‘If it’s meant to be, it’s never too late for a do-over.’ But sadly, now it is.”

“Looking back, Al admits the love of his life was Diane, who he’s always called, ‘an amazing woman,’” source added.