The pontiff's flight from Rome touched down at Dublin Airport at 10.26am.
Hundreds of thousands of people are expected to welcome Francis during his whistle-stop tour of the capital city and Co Mayo over the weekend.
In the coming 36 hours, the Pope will witness a country that has undergone seismic social changes in the four decades since the last papal visit in 1979, when John Paul II was lauded by a nation shaped by its relationship with an all-powerful Catholic Church.
Senior Irish clerics and other dignitaries gathered on the apron of the runway to greet the Pope clapped as the Alitalia flight landed.
Irish and Vatican flags were flown from the cockpit windows as the aircraft taxied toward its stand.
Pope Francis emerged from the plane soon after, walking down the steps to be greeted on a red carpet by Ireland's deputy premier and foreign affairs minister Simon Coveney, his wife Ruth and their three daughters Jessica, Beth and Annalise. The children greeted him in Irish, English and Spanish.
One of the girls then presented the Pope with a bouquet of flowers. The bouquet included thistles, yellow and white roses and green foliage.
While Francis is sure to receive a warm reception from the thousands of pilgrims who have travelled to be part of the occasion, he will also be met by protesters angry at how the church dealt with multiple clerical sex abuse scandals that have damaged trust in the religious institution and seriously weakened its influence on Irish society.
At some point over the weekend, the Pope will meet a number of abuse victims in a private meeting amid expectation he will use his public utterances elsewhere to confront the emotive issue.
The Pope was driven from the airport for a meeting with the Irish President at his residence in Dublin's
Phoenix Park.
He is due to make a speech at Dublin Castle around lunchtime on Saturday, shortly after meeting Irish Taoiseach Leo Varadkar.
Earlier this week, the Pope wrote a 2,000-word letter to Catholics in which he condemned the crime of sexual abuse by priests and subsequent cover-ups.
He demanded accountability in response to fresh revelations in Pennsylvania in the United States of decades of misconduct by clerics.
Francis is ostensibly in Ireland to attend the World Meeting of Families (WMOF) - a major global church event focused on promoting family values.
However, he will also fulfil a number of other engagements.
With Ireland in the midst of a high-profile homelessness problem, the Pope will meet a number of impacted individuals and families at a centre run by a religious order.
Tens of thousands of people are expected to line the streets of Dublin city centre on Saturday afternoon as he passes through in his famous Popemobile.
In the evening he will join 82,000 pilgrims at a musical festival in the landmark Croke Park Gaelic Athletic Association stadium.
On Sunday, the Pope will fly west to Co Mayo, where he will follow in the footsteps of John Paul II and take part in a religious service at a Holy shrine in Knock.
He will then return to Dublin for the closing centrepiece of the WMOF event - an outdoor Mass in front of an expected congregation of half a million people in Phoenix Park.
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