Goldie Hawn, Robert De Niro and more stars honor Diane Keaton after her death

Hollywood is mourning the loss of Diane Keaton.

The Oscar-winning actress, best known for her roles in "Annie Hall," "The Godfather" and "The First Wives Club," died Saturday at the age of 79.

Her death was confirmed by producer Dori Rath, who had previously worked with her. No cause of death has been released.

Goldie Hawn shared a heartfelt tribute on Instagram, posting a photo of Keaton and reflecting on their longtime friendship.

"Diane, we aren't ready to lose you," she wrote in the caption. "You've left us with a trail of fairy dust, filled with particles of light and memories beyond imagination. How do we say goodbye? What words can come to mind when your heart is broken? You never liked praise, so humble, but now you can't tell me to 'shut up' honey. There was, and will be, no one like you."Hawn reminisced about their time working together on "The First Wives Club," sharing memories of laughter and friendship on set.

"You stole the hearts of the world and shared your genius with millions, making films that made us laugh and cry in ways only you could," she wrote. "I was blessed to make 'First Wives Club' with you, our days starting with coffee in the makeup trailer, laughing and joking, right through to the very last day of filming. It was a roller coaster of love."

She continued, "We agreed to grow old together, and one day, maybe live together with all our girlfriends. Well, we never got to live together, but we did grow older together. Who knows… maybe in the next life.Shine your fairy dust up there, girlfriend. I'm going to miss the hell out of you. My heart goes out to your beautiful children, Dex and Duke. I love you."

In a statement to ABC News, Robert De Niro said he was heartbroken by Keaton's death.

"I am very sad to hear of Diane's passing," the statement read. "I was very fond of her and the news of her leaving us has taken me totally by surprise. I was not expecting her to leave us. She will be missed. May she rest in peace."

Jane Fonda also paid tribute to Keaton on Instagram, writing, "It's hard to believe...or accept…that Diane has passed."

"She was always a spark of life and light, constantly giggling at her own foibles, being limitlessly creative…in her acting, her wardrobe, her books, her friends, her homes, her library, her world view. Unique is what she was. And, though she didn't know it or wouldn't admit it, man she was a fine actress!" she added.

Bette Midler shared her own message of loss, calling Keaton "The brilliant, beautiful, extraordinary."

"I cannot tell you how unbearably sad this makes me," she wrote on Instagram. "She was hilarious, a complete original, and completely without guile, or any of the competitiveness one would have expected from such a star. What you saw was who she was…oh, la, lala!"

Viola Davis remembered Keaton as a woman who "defined womanhood."

"The pathos, humor, levity, your ever-present youthfulness and vulnerability — you tattooed your SOUL into every role, making it impossible to imagine anyone else inhabiting them," she wrote in her Instagram caption. "You were undeniably, unapologetically YOU!!! Loved you. Man… rest well. God bless your family, and I know angels are flying you home. 💔💔💔."

PETA Senior Vice President Lisa Lange also honored Keaton's legacy, highlighting her compassion for animals.

"Diane Keaton's impact as a brilliant and talented actor is undeniable, but PETA will always remember her as a true friend to animals," the statement read. "At every turn, she used her platform to champion animals, from advocating kindness toward animals often overlooked, such as pigeons, to taking on abusive cub-petting operations by endorsing the Big Cat Public Safety Act, to ditching meat and reminding everyone that 'it's nuts' to eat animals. Diane's heart was evident in everything she did, and she will be greatly missed by all of us at PETA."