The 71-year-old, who has motor neurone disease, also expressed the view in an interview with the BBC that people should not be prosecuted for helping a loved one to die.
"We don't let animals suffer, so why humans?" he said.
However, if assisted suicide were to be legalised, he said there would need to be checks in place to prevent abuse.
"I think those who have a terminal illness and are in great pain should have the right to chose to end their own life and those that help them should be free from prosecution," he said.
"But there must be safeguards that the person concerned genuinely wants to end their life and they are not being pressurised into it or have it done without their knowledge and consent, as would have been the case with me."
Hawking was once on life support in 1985 and his first wife, Jane Hawking, was given the option of switching it off but she decided against it and he recovered.
Under current law, it is illegal to assist someone in ending their life, although the Director of Public Prosecutions issued guidance last year saying it was unlikely that friends or family members would be prosecuted if they helped a loved one to die.