Marlo Thomas and Hollywood friends remember Phil Donahue as a 'pioneer'.

Tributes poured in across social media for the iconic talk show host, Phil Donahue, who was remembered as a legend in the entertainment industry.

On Sunday, the family of the Emmy Award-winning journalist announced his death after a long illness. He was 88 years old.

On Monday, Marlo Thomas honored her late husband of 40 years on Instagram by sharing a cherished photo of them riding a moped together on vacation many years ago.

"I'm sure you've heard the sad news that I lost my sweetheart last night, so I understand that I'll be taking a break from this page to focus on myself and the people who loved Phil," she wrote in the caption.

As I depart, I want to express my gratitude for the love and support you've shown me throughout my journey. Your kind words and generosity have been a source of comfort and inspiration to me. I hope you continue to find joy in life and cherish the people who matter most to you. Sending you love and good wishes, Marlo.

Donahue was referred to as the "true godfather of the talk show genre" by Montel Williams.

"Phil Donahue, the pioneer of audience participation on critical issues, has passed away. His contributions to television and dialogue on important societal topics are immeasurable. My deepest condolences go out to his family during this time. Rest in peace, Phil—you will be missed but never forgotten."

Sarah Jessica Parker expressed her love for Phil Donahue on Instagram by writing "We loved you, Phil Donahue."

"SJ honors @marlothomas and his family with sincere condolences. RIP and Godspeed. Thank you for decades of smart, funny, informative, and brave television. We honor your work and devotion to your audience."

Oprah Winfrey, an Academy Award-nominated actress and talk show host, recognized Donahue as a "pioneer" and thanked him for supporting her during the beginning of her career.

"Phil Donahue was the first to prove that daytime talk and women watching should be taken seriously, paving the way for the Oprah Show. It's with gratitude that I pay tribute to him, as he was a true pioneer. Rest in peace, Phil."

Ricki Lake expressed her admiration for Donahue and felt honored to have known him. She stated that he will be greatly missed and that he has left behind a remarkable legacy.

Michael Moore paid tribute to his "good friend" Donahue on X, formerly known as Twitter, by sharing photos of the two of them out to dinner together.

"Phil Donahue, my dear friend, has passed away. He was a fearless and brave individual who never backed down from a challenge. He gave voice to the voiceless and was removed from TV for his outspoken stand against the Iraq War. One of his best documentaries, BODY OF WAR (2007), is a testament to his talent and dedication. He was kind, giving, and relentless in his pursuit of truth and justice. He was an inspiration to many."

In 1976, Amy Sedaris posted a photo of Donahue on the cover of People Magazine, expressing her sadness, stating that her family grew up watching his show and learned a lot from it.

Questlove, a musician, stated that Donahue's influence on his perspective as a child was significant, and his passing signifies the conclusion of an era.

"Phil Donahue was the standard of the modern morning talk show for Gen X during sick days from school. He wrote, 'Who before Oprah owned the lane was the standard of the modern morning talk show in which red state & blue state America realized HOW different (& alike?) we were. Rest in peace.'"

Planet Chronicle Digital's Tracy Wright contributed to this report