Mary Tyler Moore Dies: Robert Redford, Carol Burnett and More Stars Mourn the TV Icon's Death

The iconic TV actress died at age 80 on Wednesday, ET can confirm.

Hollywood lost one of its greatest icons on Wednesday.

Mary Tyler Moore, who most notably starred in The Mary Tyler Moore Show and The Dick Van Dyke Show, died in Greenwich, Connecticut, of cardiopulmonary arrest after contracting pneumonia, Moore's rep confirms to ET. She was 80.

All over social media, messages of love and condolences have poured in honoring the beloved actress.

WATCH: Mary Tyler Moore Dies at 80

"There are no words. She was THE BEST!" Moore's longtime friend and co-star Dick Van Dyke tweeted. "We always said that we changed each other's lives for the better."

Ed Asner, Moore's TV boss on The Mary Tyler Moore Show, tweeted, "#marytylermoore my heart goes out to you and your family. Know that I love you and believe in your strength."

Robert Redford honored Moore in a statement to ET, writing, "Mary's energy, spirit and talent created a new bright spot in the television landscape and she will be very much missed. The courage she displayed in taking on a role, (Ordinary People), darker than anything she had ever done, was brave and enormously powerful."

"She will be so missed," Carol Burnett said in a statement. "She was a pioneer on television and also one of the sweetest, nicest people I ever knew."

Cloris Leachman, meanwhile, wrote, "My heart goes out to her husband, Robert—he was never more than a touch away from her. The picture that we all have of her, that’s how she was—sweet, kind, so tender, so delicate. She was America’s sweetheart. Valerie and I always had to rehearse and rehearse, to work things through but Mary was always ready to go, thoroughly prepared. The last time I saw her was our Hot In Cleveland reunion. I had a feeling I wouldn’t see her again. If I could see her one last time I’d hold her in my arms and say, 'We love you.'"

CBS CEO Les Moonves called Moore "a once-in-a-generation talent," adding, "She will be long remembered as a gifted actress, television pioneer and a role model to so many. CBS has lost one of the very best to ever grace our airwaves and our industry has lost a true legend and friend."

"We had some remarkable and unforgettable experiences together on The Dick Van Dyke Show," Moore's former co-star, Rose Marie, said in a statement to ET. "We were able to grow closer over the years and eventually became dear friends. We kept in touch until the very end. I shall miss her, very much."

"We were neighbors and lived in the San Remo for 10 years in New York," actress Michael Learned shared in a statement. "She was my lunch buddy and I loved her. My condolences to Robert."

"I am deeply saddened by the news of Mary's passing. She was a truly amazing person, a great friend, and an inspiration to all," Timothy Hutton, who played Moore's son in 1980's Ordinary People, said in a statement. "I will always be grateful for her kindness and thankful beyond words for knowing her. She will be missed greatly."

"Mary was and is and now always will be, perfect. She was the perfect actor to work with, the performance she gave was perfect, painfully perfect, and the friendship she offered was perfect. I am in her thrall," Donald Sutherland, Moore's husband in Ordinary People, mourned in a statement.

Oprah Winfrey also spoke out, telling ET in a statement, "Mary Tyler Moore majorly influenced my life and career. I respected and admired her business acumen, her passion and compassion for all life, and most importantly, the values espoused through her storytelling. I thank her for being a light that shined so brightly, it let me see myself in her."

Winfrey also tweeted, "Even now looking at this picture I want to cry. I still can't believe Mary Tyler Moore touched my face. Will love her 4 ever."

Oscar winner Michael Keaton, who appeared with Moore in her comedy variety shows Mary and The Mary Tyler Moore Hour in the late 1970s, shared his memories of the beloved actress with ET, recalling how Moore "could light up a room."

“She is an icon and a friend. She was my cast mate and my boss. She was incredibly funny and completely generous," he said. "As an actor and comedian, she allowed me and everyone to perform – letting us just do our thing without any competiveness."

"She was not only a pioneer in TV, comedy and business, but she was a role model for women in general," he added. "She built an empire with MTM Enterprises and she paved the way for our new talents like Amy [Poehler], Tina [Fey] and others. She is truly going to be missed."

Carol Channing, who starred alongside Moore in the 1967 musical Thoroughly Modern Millie, recounted the actress' absolute professionalism.

"I remember her energy and love for the craft was infectious," Channing told ET in a statement on Wednesday. "She was interested in every aspect of the production for Thoroughly Modern Millie. A true professional."

Watch What Happens Live host Andy Cohen tweeted, "RIP beautiful, upbeat, shining, glorious, wonderful, iconic Mary Tyler Moore."

Dennis Leary simply shared one of Moore's famous quotes, "You can't be brave if you've only had wonderful things happen to you."

George Takei had kind words for Moore as well, tweeting, "She turned the world on with her smile. RIP, Mary Tyler Moore. You were a role model in so many ways."

"That shift in the Earth you just felt? That crater that is left behind? That is the legacy of the incomparable #marytylermoore RIP 2 an icon," Josh Gad wrote on Twitter.

Gad shared a lengthier tribute on Instagram, writing, "Comedic brilliance. Creative Trendsetter. Feminist Icon. Titanic Talent. One-of-kind. There is no such thing as hyperbole when describing #marytylermoore and the #marytylermooreshow - her person has left us but her persona will shine on for generations to come."

Britney Spears also took to Twitter to honor Moore, writing, "So strong, so courageous and so beautiful. Rest In Peace, Mary Tyler Moore."

EXCLUSIVE: Dick Van Dyke Says He and Mary Tyler Moore Had a 'Teenage Crush' on Each Other

Read on to see how more celebs paid tribute to the celebrated star.

EXCLUSIVE: Dick Van Dyke Says He Once Thought Mary Tyler Moore Was Too Young to Play His Wife

RIP, Mary Tyler Moore.

Watch the video below for more on her death.