"I regard the brain as a computer which will stop working when its components fail," he told the Guardian's Ian Sample. "There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark."
Hawking, 69, who has survived for nearly five decades with a motor neurone disease that doctors believed would kill him while he was still in his early 20s, said he does not fear death. He also said that having lived with the prospect of death from his incurable illness has ultimately led him to enjoy life more.
"I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first," he said.
Hawking was the target of criticism from religious circles when his most recent book, "The Grand Design," argued that there was no need for a creator to explain the universe's existence.
In the Guardian interview - conducted in advance of his lecture at this week's Google Zeitgeist meeting in London, where he will address the question: "Why are we here?" - Hawking rejects an afterlife and emphasizes the need for people to realize their full potential on Earth.
When asked what is the value of knowing why are we here, Hawking replied, "The universe is governed by science. But science tells us that we can't solve the equations, directly in the abstract. We need to use the effective theory of Darwinian natural selection of those societies most likely to survive. We assign them higher value."
When asked what he found most beautiful in science, Hawking said, "Science is beautiful when it makes simple explanations of phenomena or connections between different observations. Examples include the double helix in biology, and the fundamental equations of physics."
Hawking said that our existence is down to pure chance, and that one's goal should be to "seek the greatest value of our action."