Pope Benedict XVI has attacked the commercialisation of Christmas, as he held the traditional Christmas Eve Mass at St Peter's Basilica in Rome.
In his homily, he urged worshippers to "see through the superficial glitter of this season and to discover behind it the child in the stable in Bethlehem".
The Pope also lamented the enduring presence of violence in the world.
The pontiff will deliver his annual Urbi et Orbi (To the City and the World) speech in a few hours.
Meanwhile, Christian pilgrims and tourists from around the world last night converged on Bethlehem for Christmas.
Celebrations culminated in Midnight Mass at the 1,700-year-old Church of the Nativity, built on the spot where it is believed Jesus was born.
About 120,000 visitors were in the Palestinian West Bank town, 30% up on last year, officials said.
Christmas Eve Mass in Rome was brought forward two hours to 22:00 local time (21:00 GMT) from midnight - in order to spare Benedict a late night.
Wearing cream and gold vestments, the Pope, who is 84, proceeded slowly up the aisle of St Peter's on a mobile platform.
In his homily, he urged the faithful to focus on the story of Jesus' birth, saying this would help "find true joy and true light".
He also prayed for those who would spend this Christmas in poverty and suffering.
Even if he is physically more frail now, his message was firm, the BBC's Alan Johnston in Rome says.
In a few hours, the pontiff will give his traditional blessing and message in St Peter's square before tens of thousands of people from around the world.
In Bethlehem, the Latin Patriarch of Jerusalem, Fuad Twal, led the Midnight Mass.
He passed through the massive gate in the controversial Israeli barrier that separates Jerusalem from Bethlehem and arrived in Manger Square, where he was greeted with a bagpipe band.
Patriarch Twal, a Palestinian who is a Jordanian citizen, has expressed concern for Christians in the current upheavals in the Middle East and asked them to support moves towards freedom and democracy.
His midnight homily urged "the return of calm and reconciliation in Syria, in Egypt, in Iraq and in North Africa".
It reads: "O Child of Bethlehem, in this New Year, we place in your hands this troubled Middle East and, above all, our youth full of legitimate aspirations, who are frustrated by the economic and political situation, and in search of a better future."
American visitor Irma Goldsmith told Associated Press: "I watch Christmas in Bethlehem each year on TV, but to be here in person is different. To be in the spot where our saviour was born is amazing."
Palestinian President Mahmoud Abbas attended the celebrations.
He said: "I wish for the Palestinian people that next year will be the year of implementing peace in the occupied Palestinian lands."
Bethlehem Mayor Victor Batarseh also said he hoped the festivities would bring Palestinians closer to their dream of statehood.