It is only the fourth visit by a Pope to the majority Islamic country.
The pontiff is expected to raise the issue of Muslim-Christian relations, in the wake of the rise of Islamic State in neighbouring Syria and Iraq. Turkey is estimated to hold around 2 million Syrian refugees.
During his visit, Pope Francis will meet with Turkish President Recep Tayyip Erdogan at his new palace in the capital of Ankara.
He's then expected to travel to Istanbul, visiting heritage sites from the Byzantine and Ottoman empires, and meeting with Orthodox Ecumenical Patriarch Bartholomew I.
Vatican Radio correspondent Philippa Hitchen is travelling with the Pope and said during an interview that his visit has "political" and "religious" dimensions:
"The Pope will say very clearly once again, I'm sure, that no believer, nobody who has any faith in God can ever carry out any acts of violence in the name of religion."
The 77-year-old has already condemned the "distortion and manipulation" of religious beliefs by extremists and expressed concern that Christian communities risk being 'wiped out' in parts of the Middle East.
Earlier this week, the pontiff mentioned the possibility of peace negotiations with Islamic State militants.
Despite admitting such talks would be unlikely, he said: "I'll never count anything as lost. Never.
"Never close the door. It's difficult, you could say almost impossible, but the door is always open."
International lawyer and church consultant Harry Hagopian is an expert on the Middle East:
"In a Muslim country it is inevitable that there are some times when some of those Christian communties feel somewhat harrassed, but at other times they just get on with their lives.
"There is a very strong history of Christianity which was over a streach of centuries. At the moment that is not the case.
"The real change started taking place since the first world war. At the moment Turkey has a different texture to it, and I think the Pope is going there with that very much with in mind.
He will have to deal with the reality today, not with what was there 200 years ago"
Listen to the full interview with Dr Hagopian with Premier's Paul Hutton.
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