Pope Benedict will resign on February 28 citing health concerns, according to his spokesman Father Frederico Lombardi.
The 85-year-old told his senior clergy that because of his advanced age and diminishing strength, he didn't feel he could carry on the job.
He has served as pope since April of 2005.
The pope is quoted as saying he is "fully aware of the gravity of his resignation"
Resigning means the Catholic Church will be without a pope for a period of time until a new one is selected.
The cardinals say they expect to hold a conclave to elect a new pope before the end of March.
The 265th Pontiff, Benedict is the first pope to resign in 600 years.