Pope Francis, celebrating his first Christmas as the head of the Catholic Church leader, this morning called for dialogue to end the conflict in South Sudan and all wars.
He said everyone should strive to be personal peacemakers.
Speaking to tens of thousands of people from the central balcony of St Peter's Basilica, the same spot where he emerged to the world as pope when he was elected on 13 March.
He also made another appeal for the environment to be saved from "human greed and rapacity".
The leader of the 1.2 billion-member church wove his first "Urbi et Orbi" (to the city and world) message around the theme of peace.
He called for "social harmony in South Sudan, where current tensions have already caused numerous victims and are threatening peaceful coexistence in that young state".
Thousands are believed to have died in violence divided along ethnic lines between the Nuer and Dinka tribes in the country, which seceded from Sudan in 2011 after decades of war.
He also called for dialogue to end the conflicts in Syria, Nigeria, the Democratic Republic of Congo and Iraq, and prayed for a "favourable outcome" to the peace process between Israelis and Palestinians.
"Wars shatter and hurt so many lives," he said, saying their most vulnerable victims were children, the elderly, battered women and the sick.
The thread running through the message was that individuals had a role in promoting peace, either with their neighbour or between nations.
The message of the birth of Jesus in Bethlehem was directed at "every man or woman who keeps watch through the night, who hopes for a better world, who cares for others while humbly seeking to do his or her duty," he said.
"God is peace: let us ask him to help us to be peacemakers each day, in our life, in our families, in our cities and nations, in the whole world," he said.
Last night, the Pope, celebrating his first Christmas as leader of the world's 1.2 billion Catholics, urged people to shun pride and selfishness and open up their hearts to God and their fellow man.
He celebrated a solemn Christmas Eve mass for 10,000 people in a packed St Peter's Basilica as hundreds of others watched on mega-screens in the square outside.
The great bells of the basilica, the same that rang to announce his election on 13 March, sounded when the Sistine Chapel Choir intoned the Gloria.
The prayer begins with the words the Bible says angels sang on the night Jesus was born in Bethlehem.
The Pope, who concelebrated the mass with more than 300 cardinals, bishops and priests, urged people not to be afraid to reach out to God.
"Do not be afraid! Our Father is patient, he loves us, he gives us Jesus to guide us on the way which leads to the promised land.
"Jesus is the light who brightens the darkness. He is our peace," he said.
Meanwhile, Catholic Archbishop of Dublin Dr Diarmuid Martin told those attending midnight mass at St Mary’s Pro-Cathedral in Dublin last night that Christmas is a feast of humanity and spontaneously releases generosity in people.
In a sermon at Christ Church Cathedral this morning, Church of Ireland Archbishop Dr Michael Jackson spoke of the need to grapple with the word incarnation, which is about change and making new things happen.
He said incarnation offers human and divine goodness in the face of institutional evil and corruption.