"We ask for peace, above all, for Syria and Iraq, that the roar of arms may cease and that peaceful relations may be restored among the various groups which make up those beloved countries," the pontiff said.
The Holy Father was speaking to tens of thousands of people after presiding over Mass in a wet St Peter's Square.
He said the world must not stand by and do nothing whilst Christians were being killed for their faith in Iraq and Syria.
Tens of thousands of believers have been forced to flee their homes in the region as Muslim militant group Islamic State takes over large parts.
Francis said: "May the international community not stand by before the immense humanitarian tragedy unfolding in these countries and the drama of the numerous refugees.
"From the risen Lord we ask the grace not to succumb to the pride which fuels violence and war, but to have the humble courage of pardon and peace.
"We ask Jesus, the Victor over death, to lighten the sufferings of our many brothers and sisters who are persecuted for his name, and of all those who suffer injustice as a result of ongoing conflicts and violence."
He also spoke of the need to find peace in parts of Africa to stop Christians being persecuted for their beliefs.
"We pray for peace for all the peoples of the Holy Land. May the culture of encounter grow between Israelis and Palestinians and the peace process be resumed, in order to end years of suffering and division.
"We implore peace for Libya, that the present absurd bloodshed and all barbarous acts of violence may cease, and that all concerned for the future of the country may work to favour reconciliation and to build a fraternal society respectful of the dignity of the person.
"For Yemen too we express our hope for the growth of a common desire for peace, for the good of the entire people.
"We ask the risen Lord for the gift of peace for Nigeria, South Sudan and for the various areas of Sudan and the Democratic Republic of the Congo."
Pope Francis again condemned Thursday's massacre in Kenya.
"May constant prayer rise up from all people of goodwill for those who lost their lives, I think in particular of the young people who were killed last Thursday at Garissa University College in Kenya," he said.
The Pope also prayed for peace in Ukraine and for an end to arms and people trafficking.