Pope Francis was admitted to a Rome hospital on Sunday afternoon for "scheduled surgery" on his colon later in the day, the Vatican said.
Spokesman Matteo Bruni said the pope, 84, was suffering from "symptomatic diverticular stenosis" of the colon, a condition that can cause recurrent abdominal pain, bloating and changes in bowel habits.
Bruni said the operation would take place later on Sunday in Rome's Gemelli hospital, which is the institution where popes receive medical treatment. Another statement would be issued afterwards.
It is the first time the pope has been admitted to hospital since his election in 2013.
The pope appeared to be in fine health several hours earlier when he addressed thousands of people in St. Peter's Square for his Sunday blessing and announcing a trip to Slovakia and Budapest for September.
Francis is sometimes short of breath because a part of one of his lungs was removed following an illness when he was a young man in his native Argentina.
Francis also suffers from sciatica, a condition that causes pain that radiates from the lower back along the sciatic nerve to the legs.
He is sometimes seen walking with difficulty because of the pain and receives regular physical therapy for it.
The condition forced him to miss several events at the beginning of this year.
Last year, a bad cold kept him from taking part in a week-long Lenten retreat with his with senior aides south of Rome.
In 2014, a year after he was elected pope, Francis was forced to cancel several engagements because of what was believed to be a stomach ailment.