Pope Francis has met the grand imam of Cairo's al-Azhar mosque after a five-year pause in dialogue between the Roman Catholic Church and the mosque, the highest authority of Sunni Islam.
Sheikh Ahmed al-Tayeb visited the Vatican en route to a Paris conference involving Muslims and Catholics.
Al-Azhar froze meetings in 2011 after taking offence at some comments made by the previous pope.
It said Pope Benedict made "repetitive and negative statements" about Muslims.
At the start of the half-hour meeting on Monday, the Pope said that the fact it was taking place at all was significant.
"The meeting is the message," he said.
Relations between Al-Azhar and the Vatican soured in 2006 after Pope Benedict quoted a 14th Century Byzantine emperor in remarks taken by some Muslims to imply that Islam was a violent religion.
Pope Benedict repeatedly said the words did not reflect his personal views, but he stopped short of issuing a clear apology to Muslims.
On Monday, a Vatican spokesperson told AFP news agency that the meeting between Sheikh Tayeb and Pope Francis had been "very cordial".
The leaders exchanged gifts, embraces and discussed conflicts and tensions between Christians and Muslims in the Middle East.