Macdonald died on Tuesday at the age of 61 following a private battle with cancer, his manager Marc Gurvitz confirmed.
Macdonald was best known as the host of Weekend Update on Saturday Night Live from 1993 to 1998. He also starred in films Billy Madison, Dirty Work, Deuce Bigelow, Screwed and voiced Lucky the Dog in the Dr. Dolittle series of films.
He additionally had a sitcom titled Norm that lasted three seasons, his podcast Norm Macdonald Live and a Netflix talk show that ran for one season in 2018.
"Every one of us loved Norm. Some of the hardest laughs of my life with this man. Most fearless funny original guy we knew. An incredible dad. A great friend. A legend. Love u pal," Sandler said on Twitter, alongside a photo of himself with Norm on the set of Billy Madison.
"Norm was in a comedy genre of his own. No one like him on this planet. Please do yourself a favor and watch his stuff. He was one of a kind of all time," Silverman said on Twitter.
"In every important way, in the world of stand-up, Norm was the best. An opinion shared by me and all peers. Always up to something, never certain, until his matter-of-fact delivery leveled you," Letterman said on Twitter.
"I was always delighted by his bizarre mind and earnest gaze. (I'm trying to avoid using the phrase, 'twinkle in his eyes'). He was a lifetime Cy Young winner in comedy. Gone, but impossible to forget," Letterman continued.
"You were unmistakably intelligent -- your comedy and the way you cared so much about words and sentences and storytelling was like no one else. Just brilliant," Molly Shannon said in a lengthy post on Instagram, alongside an SNL cast photo including herself and Macdonald.
"You were one of a kind with a twinkle in your eyes. And a lot of people don't know this but Norm was a math genius. Great father and friend, old time elegance.....love ya baby," Shannon continued.
"I am absolutely devastated about Norm Macdonald. Norm had the most unique comedic voice I have ever encountered and he was so relentlessly and uncompromisingly funny. I will never laugh that hard again. I'm so sad for all of us today," Conan O'Brien said on Twitter.
"Norm, I didn't just like you. I love you. You didn't just make me laugh. You made me cry with laughter. I'm still crying today. But when I think of you, my tears run down my face with all the memories of all the laughter and all the joys that you brought to all of us," Rob Schneider said on Twitter, alongside photos of himself with Macdonald, Sandler, David Spade and Tim Meadows.
"Oh [expletive]. I was a huge fan of Norm Macdonald and I essentially ripped off his delivery when I first started acting. I would stay up specifically to watch him on talk shows. He was the funniest guest of all time. We lost a comedy giant today. One of the all time greats. RIP," Seth Rogen said on Twitter.
"Devastated. Met Norm in Ottawa when he was in my audience at 17 years old. Been close friends for decades. We have lost a comedic genius. No other voice in comedy has been as uniquely prolific, brazen, dark, hilarious, and heartfelt. Love you forever, Norm," Bob Saget said on Twitter alongside a selfie he took with Macdonald.