Williams died Monday at his California home of an apparent suicide. He was 63.
"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," Obama said in a statement released Monday night. "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 Obama family offers our condolences to Robin’s family, his friends, and everyone who found their voice and their verse thanks to Robin Williams."