Clarke had been wheelchair-bound for several years with complications stemming from a youthful bout with polio and had suffered from back trouble recently, said Scott Chase, the secretary of the nonprofit Arthur C. Clarke Foundation.
He died early Wednesday -- Tuesday afternoon ET -- at a hospital in Colombo, Sri Lanka, where he had lived since the 1950s, Chase said.
"He had been taken to hospital in what we had hoped was one of the slings and arrows of being 90, but in this case it was his final visit," he said.
In a videotaped 90th birthday message to fans, Clarke said he still hoped to see some sign of intelligent life beyond Earth, more work on alternatives to fossil fuels -- and "closer to home," an end to the 25-year civil war in Sri Lanka between the government and ethnic Tamil separatists.
Clarke's contributions to the world of science fiction-and the imagination of young boys and girls-is simply unfathomable. He is best known as the writer of "2001: A Space Odyssey" and its sequels, but he is also well known for novels such as "Rendezvous with Rama" and "Childhood's End" (one of my all-time science fiction favorites) and he will be remembered as one of the greatest authors not only of the "Golden Age" of Science Fiction, but of all time. I doubt I'm speaking for us here alone when I say that he will be dearly, dearly missed.
UPDATE: The NY Times has a good portrait of Clarke's life and work here.