Pictures show the Pope and María Corina Machado, a Nobel Peace Prize recipient, shaking hands and talking in the Pope's private library.
The visit appeared to be unexpected; it had not been announced in advance. Even after the meeting, the Vatican did not share any details, several media outlets reported.
Machado received the Peace Prize in Oslo in December, but her whereabouts have been unknown since then.
The audience at the Vatican took place on the same day Italy's foreign minister announced that two Italian citizens had been released from captivity in Venezuela and were on their way home.
A total of 116 political prisoners in Venezuela have been released since last week, Venezuelan authorities said on Monday, though opposition groups and human rights organizations reported lower figures.
