Emma Thompson -- who appeared in numerous films with Rickman, including Love Actually, Sense and Sensibility, Judas Kiss, three Harry Potter films and the TV movie The Song of Lunch -- said that she felt "hugely privileged to have worked" with the actor.
"Alan was my friend and so this is hard to write because I have just kissed him goodbye," the 56-year-old actress said in a statement. "What I remember most in this moment of painful leave-taking is his humor, intelligence, wisdom and kindness. The intransigence which made him the great artist he was -- his ineffable and cynical wit, the clarity with which he saw most things, including me, and the fact that he never spared me the view."
Thompson -- who was also directed by Rickman in the 1997 film The Winter Guest -- added, "I learned a lot from him. He was the finest of actors and directors. I couldn't wait to see what he was going to do with his face next. I consider myself hugely privileged to have worked with him so many times and to have been directed by him."
Helen Mirren stars alongside Rickman in his final film, Eye in the Sky -- which will be released in the U.S. on March 11 -- and she shared her heartfelt memories of the actor in a statement to ET.
"Alan was a towering person, physically, mentally and as an artist," the 70-year-old actress said. "He was utterly distinctive, with a voice that could suggest honey or a hidden stiletto blade, and the profile of a Roman Emperor. He was also a great friend, generous and social. He will be very missed by many."
Many more of Rickman's co-stars, including his Harry Potter collaborators, and directors took to social media to honor the late actor. His Galaxy Quest co-stars, Sigourney Weaver and Tim Allen both shared their condolences, as did Lee Daniels who directed Rickman in Lee Daniels' The Butler, shared a tribute on Instagram.
"Alan's enormous strength of character infused every character he played. Who else could have brought such pain and wit to Snape," Weaver said in a statement, referencing Rickman's role in the Harry Potter franchise. "He used his talent always to make a difference, his production of Rachel Corrie being one of the most powerful examples. I can't believe he's gone."
Kevin Smith, who directed Rickman in Dogma, also shared his heartfelt memories and condolences on Facebook. "Alan was the first non-friend who signed up to the flick, but he became a great friend in record time... Thank you for lending a hack like me your artistry and your credibility, Alan," Smith wrote of Rickman, who portrayed the voice of God, Metatron, in the 1999 film.
"You were never Snape to me as much as you were the adult Harry Potter himself: a bonafide wizard who could conjure absolute magic using merely words. He was a HUGE cauldron of win, this man," Smith ended his message. "I'll miss him forever. Rest in Peace, Voice of God. Back to Heaven, where you came from..."
Hugh Jackman also praised his friend after hearing the news of his death. "Alan Rickman. Amazing actor and director," he posted on Facebook. "Above all the most generous, funny, loving friend to Deb and I. We will miss you so."
Here's how other stars have reacted to the loss:
Feel so lucky to have worked with the legendary #alanrickman. May your continued journey take you to extraordinary places. #gonetoosoon #rip