Michel Lapointe is a convicted drugs gang member arrested in 2006 who weighs 450lb (205kg).
He could not fit on the chair in his Montreal prison cell and his body protruded six inches on either side of his bed, press reports said.
Officials ruled that Lapointe’s prison conditions were “difficult” because of his health.
The Journal de Montreal newspaper quoted a letter from the authorities to Mr Lapointe saying: “You have been detained for more than 25 months and your prison conditions are difficult because of your health.”
They also cited the refusal of two other facilities to accept the 37-year-old, who was handed a five-year sentence in May this year.
Mr Lapointe was freed late on Tuesday.
“I’m going to have a proper bed and finally have a chair I can sit in,” he told the paper outside the prison.
“I want a normal life. I’ve done some stupid things and I’ve paid for them,” he added.
