"Because there is a law such as gravity, the Universe can and will create itself from nothing. Spontaneous creation is the reason there is something rather than nothing, why the Universe exists, why we exist," he writes in "The Grand Design", which is being serialized by The Times newspaper.
"It is not necessary to invoke God to light the blue touch paper and set the Universe going," added the wheelchair-bound expert.
"That makes the coincidences of our planetary conditions - the single Sun, the lucky combination of Earth-Sun distance and solar mass - far less remarkable, and far less compelling as evidence that the Earth was carefully designed just to please us human beings," he wrote.
Hawking argued earlier this year that mankind's only chance of long-term survival lies in colonizing space, as humans drain Earth of resources and face a terrifying array of new threats. He also warned in a recent television series that mankind should avoid contact with aliens at all costs, as the consequences could be devastating.