"We throw this word around too much but Regis Philbin was a legend," tweeted Chris Harrison, host of "The Bachelor."
"He was a true gentleman I’m glad I got to know and a TV host I admired and was honored to follow. Much like Arnold Palmer everybody has a great 'Regis' story, I’m grateful I have mine."
Award-winning actor William Shatner tweeted that he was "saddened to hear about" Philbin's passing. "Condolences to his wife Joy." Other iconic entertainers like Billy Crystal and Larry King also commemorated Philbin on Twitter.
His former co-hosts Kelly Ripa and Kathie Lee Gifford both effusively praised Philbin after his death. "REGIS. There will never be another," Gifford wrote.
"We are beyond saddened to learn about the loss of Regis Philbin. He was the ultimate class act, bringing his laughter and joy into our homes everyday on Live for more than 23 years," read a joint statement from Ripa and Ryan Seacrest, one of Philbin's successors on "Live."
"We were beyond lucky to have him as a mentor in our careers and aspire everyday to fill his shoes on the show. We send our deepest love and condolences to his family and hope they can find some comfort in knowing he left the world a better place."
Former football player Michael Strahan, Philbin's initial replacement on "Live," tweeted: "I’m absolutely heartbroken. Regis was an incredible man who could light up any room. He always made me feel special no matter if I saw him in the studio or ran into him on the street. Legend and Icon aren’t strong enough words to describe him. He will never be forgotten!!"
"I truly believed that #RegisPhilbin would be a presence with us forever. He was a fun, funny, charming man," "Seinfeld" actor Jason Alexander said. "On the occasions I got to be with him, he was always a bright light, endlessly interesting and interested in everyone. Sympathy to his loved ones."
Others, including Bob Saget and Jimmy Kimmel joined in, describing Philbin as "a tremendous amount of fun," among other things.
On Instagram, "Today" host Hoda Kotb wrote she was "heartbroken," alongside a photo of Philbin with Gifford, who co-hosted shows with both of them.
Several big names in show business posted photos Philbin. "I’m so sad to hear this news," former "Today" host Katie Couric said in a photo caption on Instagram.
Philbin, 88, died of natural causes Friday night, just over a month before his 89th birthday, according to a statement from his family provided to Fox News by manager Lewis Kay.
Celebrities routinely stopped by Philbin’s eponymous syndicated morning show, but the show's heart was during the first 15 minutes, when he and co-host Kathie Lee Gifford -- on “Live! with Regis and Kathie Lee” from 1985 to 2000 -- or Kelly Ripa, who co-hosted "Live!" with him from 2001 until his 2011 retirement -- bantered about the events of the day. Viewers laughed at Philbin’s mock indignation over not getting the best seat at a restaurant the night before or being henpecked by his partner.
Media figures and politicians joined in commemorating the prolific entertainer.
"RIP Regis Philbin," CNN anchor Jake Tapper said.
New York City Mayor Bill de Blasio tweeted: "Regis Philbin brought humor, warmth and wit into so many homes. Many people who never met him feel as though they’ve lost a personal friend and that’s a testament to his character. He will be missed."
The Associated Press contributed to this report.