"The pope announced that he will leave his ministry at 8:00 pm (1900 GMT) on February 28," said the spokesman, Federico Lombardi.
Last year the Pope started using a cane on occasions and recently he appeared to have trouble reading the text of an address he delivered in Rome.
There was no immediate official comment from the Vatican.
In November last year, he declared that it is "beautiful to be old".
"The quality of a society, I'd say of a civilisation, is judged by how well it treats its elderly," the 85-year-old pontiff said during the visit to the home run by the Saint Egidio Community, a Catholic charity.
While it was "beautiful to be old", age brought challenges and difficulties with which he himself was familiar.
"I know well the difficulties, the problems and the limits of this age, and I know that these difficulties are aggravated for many people by the economic crisis," the Pope said.