It will cost €2 and the money will go towards maintaining the former Pagan temple, which has been a church since AD 609.
Those attending religious services will also still be able to go without paying.
The building is famous for its circular skylight and being the burial site of the Renaissance artist Raphael.
The oldest parts of the building date back to the 2nd Century under Emperor Hadrian.
The popular location for those on tours of Rome attracted 7.4 million visitors last year.
