Security was tight at the hill-top shrine following a series of attacks in Europe, with a highly visible police and army presence on the roads leading into the city, where hundreds of thousands of pilgrims were gathered.
Francis hopped in an open-topped pope mobile for a tour through the cheering crowds.
'We slept so little, but it's worth it, what an atmosphere!' said pilgrim Kate Tor, whose young sons were among the thousands of children who had camped out on the sweeping avenue leading to the monastery.
Teenagers still wrapped in sleeping bags, elderly couples perched on folding chairs outside tents and families with Francis-themed balloons were serenaded by the Argentine pope's favourite tango music before his arrival.
The pontiff, in Krakow to headline an international Catholic youth extravaganza, travelled to the southern city to pray before the legendary Black Madonna and say mass
The Pope was helped to his feet and was uninjured despite the tumble. He went on the finish Mass, which was aired to millions on television
Francis fell onto his back on to the carpeted floor and had to be quickly helped to his feet by those around him this morning
Francis suffers from sciatica, a medical condition in which pain sometimes shoots down the leg from the lower back. He was uninjured and finished the event, which was aired to a television audience of millions
Pope Francis takes a fall at the beginning of the Holy Mass in the Shrine of Czestochowa on the occasion of the 1,050th anniversary of the baptism of Poland
Ambulances and fire-engines were on standby with Polish officials taking no chances with security following the jihadist murder of a priest in a French church on the eve of the five-day trip to celebrate the 2016 World Youth Day.
Arriving on Wednesday, the Argentine said the world was at war but argued that religion was not the cause, insisting the way for people to 'overcome fear' was to provide asylum to those fleeing war and persecution.
He led a mass to mark the 1050th anniversary of Poland's Catholic faith at the monastery.
The Black Madonna has been venerated since 1711, when the bubonic plague decimated Warsaw's population but stopped dead when it reached the Jasna Gora monastery in the south of the country.
Since then the figure, which legend has it was painted by Saint Luke the apostle, has been hailed as miraculous.
Outdoors, the Argentine said Mass for a congregation numbering in the tens of thousands, thanking Poles for holding on to their faith in difficult times
Pope Francis managed to get back up on to his feet with a little help from those around him, including Vatican Master of Ceremonies, Guido Marini
Popular: Tens of thousands of worshippers gathered in the city of Czestochowa in Poland as they waited for Pope Francis to appear
Pope Francis leads a mass at the Jasna Gora Monastery in Czestochowa, Poland. He is visiting Poland for an international Catholic youth festival
Greeting the crowds: Pope Francis waves as he leaves Jasna Gora monastry prior to a Holy Mass in Czestochowa, Poland
Pope Francis' five-day-long visit to Krakow is in connection with the 31st World Youth Day event that ends July 31
Pope Francis has praised native son St. John Paul II as a 'meek and powerful" herald of mercy as well as countless 'ordinary yet remarkable people' who held firm to their Catholic faith throughout adversity in the former Communist-ruled nation
Francis was due to return to Krakow after the mass, where he will be presented with the keys to the city by the mayor, before jumping on to a tram which will whisk him to the sprawling Blonia meadow for his first big WYD event
Two scars on the Madonna's face were reportedly inflicted during an attempted robbery in 1430, with the petrified thieves turning tail and fleeing when blood poured from the torn painting.
Francis was due to return to Krakow after the mass, where he will be presented with the keys to the city by the mayor, before jumping on to a tram which will whisk him to the sprawling Blonia meadow for his first big WYD event.
Some 15 disabled youngsters and their families will take the tram with the pontiff to the welcome ceremony, where hundreds of thousands of people will have spent the day being entertained by singers and dancers.
The pontiff had called for a minute's silence on Wednesday evening for a Polish volunteer, Maciej Szymon Cieslam, who was to have travelled with him on the tram, but had died at the start of the month after a battle with cancer.
At his first evening appearance at the window of the archbishop's palace in Krakow, he told the thousands of youngsters gathered below that Ciesla was getting ready to party with them at the WYD in spirit.
'Now go and do your duty, make noise all night long!' he finished with a grin.
Read more: http://www.dailymail.co.uk/news/article-3712379/Moment-Pope-Francis-FALLS-Mass-TV-audience-half-million-people-visiting-Poland-s-holiest-site.html#ixzz4FhmgiGlC
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