Pope Benedict XVI will begin the traditional celebration of Christmas Eve Midnight Mass at 10:00 p.m. (2100 GMT) Monday in St. Peter's Basilica.
The 85-year-old pontiff is continuing the practice of the past three years by starting the celebration of Midnight Mass two hours early to avoid exhausting himself ahead of the full slate of activities he has planned for Christmas Day.
Thousands of the faithful from around the world are expected to attend Midnight Mass, with the free passes for the traditional rite all given out days ago.
Numerous cardinals, bishops and other members of the clergy will help the pope celebrate the Mass.
Since Midnight Mass takes several hours to celebrate, Cardinal Tarcisio Bertone, who serves as the Vatican's secretary of state, will celebrate Christmas Mass at St. Peter's Basilica on Tuesday to avoid putting too much of a strain on the elderly pope.
Benedict XVI will return to the Vatican at noon on Tuesday to read the traditional papal Christmas Message and deliver the Urbi et Orbi - Latin for "To the City and to the World" - blessing, which will be carried by about 100 television networks in more than 50 countries. EFE