Pauly Shore, Denise Austin and Ricki Lake are among the celebrities mourning the loss of Richard Simmons after his sudden death on Saturday.

Simmons, who was known for his "Sweatin' to the Oldies" workout videos, died one day after celebrating his 76th birthday. Simmons' longtime representative, Tom Estey, confirmed his death to Fox News Digital.

After news of Simmons' death broke, Shore took to X to pay tribute to the fitness guru, who he described as "one of a kind."

richard simmons portrait

Celebrities are mourning the loss of Richard Simmons after the fitness icon died on Saturday at the age of 76. ( Harry Langdon/Getty Images)

"I just got word like everyone else that the beautiful Richard Simmons has passed," the 56-year-old comedian wrote.

RICHARD SIMMONS, FITNESS ICON, DEAD AT 76

He continued, "I hope you’re at peace and twinkling up in the heavens. Please give my mother Mitzi and my father Sammy a big hug and a kiss for me." 

"You’re one of a kind, Richard. An amazing life. An amazing story. They broke the dolphin shorts when they made you. Rest in peace, my friend. Rest in peace."

Shore is set to star as Simmons in an upcoming biopic that is being produced by Warner Bros. subsidiary the Wolper Organization and written by Jordan Allen-Dutton. 

In April, Simmons expressed his disapproval of the project, which he said "did not have my blessing." Though Shore claimed that he was "up all night crying" due to Simmons' reaction, he confirmed in May that the project is moving forward.

Denise Austin, a longtime friend of Simmons, honored the late aerobics instructor in a heartfelt post on Instagram.

"My heart is hurting that my dear friend and colleague, Richard Simmons, has passed away," she wrote alongside an image of the two beaming as Austin pumped her fist.

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"I am heartbroken, as he is someone l have known and started the aerobics business with over 40 years ago," Austin continued. "Every time we were together we had so much fun… filled with hugs, laughter and tears.. ill never forget Richard singing through the hallways, hugging my daughters, and even to sending me a letter when my mom passed. 

"I cherished our friendship- and I can’t believe I just reached out less than a month ago. Richard- you have left an impact on us all. Thank you for all your love.. we did so much together in this life. I love you so much. You will forever be in my heart!! Love, Denise."

Ricki Lake posted a photo of herself posing with Simmons and Maria Menounos, writing "My heart is broken with the loss of this super special human. May he RIP."

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"I loved him so much," the 55-year-old TV personality added with a broken heart emoji. 

Simmons made appearances on Lake's former talk show "The Ricki Lake Show," which ran from 1993 to 2004.

Sally Jessy Raphael honored Simmons on X as she posted a throwback photo of herself with the "Weight Saint," a moniker that the fitness coach used on his social media accounts.

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"I am completely devastated at the loss of @theweightsaint… we’ve done so many shows together, shared so many laughs & hugs, and I considered him a dear friend who changed so many lives over the years," wrote Raphael, 89, who hosted the long-running tabloid talk show "Sally" which was originally named "The Sally Jessy Raphael Show."