President Obama called Robin Williams "one of a kind" who shared his talent "freely and generously with those who needed it most."
Williams was pronounced dead at his home in California on Monday and officials said it appeared to be a suicide.
Mr. Obama referenced many of Williams' memorable movie roles -- ones in "Mork & Mindy," "Hook," "Mrs. Doubtfire" and "Aladdin" among them -- and offered condolences to the actor-comedian's loved ones.
"Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between. But he was one of a kind. He arrived in our lives as an alien -- but he ended up touching every element of the human spirit. He made us laugh. He made us cry. He gave his immeasurable talent freely and generously to those who needed it most -- from our troops stationed abroad to the marginalized on our own streets," the president said. "The Obama family offers our condolences to Robin's family, his friends, and everyone who found their voice and their verse thanks to Robin Williams."
Many others have spoken out in tribute to Williams, including stars like Steve Martin, Henry Winkler, Sarah Michelle Gellar and Conan O'Brien. His daughter, Zelda Williams, also shared an emotional message dedicated to him.