Francis said he was committed to ridding the church of this "scourge" no matter the moral cost or amount of suffering.
With the reverberations of a litany of church sex abuse scandals casting a shadow over the first papal visit to Ireland in nearly 40 years, Francis confronted the issue in his address inside the castle's St Patrick's Hall.
Earlier, the Irish prime minister and taoiseach, Leo Varadkar, had boldly asked him to ensure that "from words, flow actions".
Pope Francis vowed on Saturday to end the sexual exploitation of children by clergy during a highly-charged visit to once deeply Catholic Ireland and, according to victims, said the corruption and cover up of abuse amounted to human excrement.
"I can not fail to acknowledge the grave scandal caused in Ireland by the abuse of young people by members of the church charged with responsibility for their protection and education", Francis told a room filled with members of the Irish government, other lawmakers and diplomats.
Pope Francis marked the first papal visit to Ireland in almost four decades with a speech acknowledging the "failure" of the Catholic Church to address the "repugnant crimes" of clerical sexual abuse there, which he said has "rightly given rise to outrage".
"I'm delighted he is coming, I think it makes a great change from the last few years of bad news for the Church", said Dubliner Kyle O'Sullivan.
The protest invites anyone who has "been harmed or abused by the Roman Catholic Church or who wishes to stand in solidarity with those harmed by its actions" to join the event at 3 pm at The Garden of Remembrance in Dublin.
A spokesman said he spent 90 minutes with them.
"There are dark aspects of the Catholic Church's history, as one of our bishops recently said".
Colm O'Gorman of Amnesty International Ireland, who was abused by a priest for more than two years as a teenager, said the Pope's comments did not go far enough.
More than three-quarters of Ireland's population flocked to see Pope John Paul II in 1979 when divorce and contraception were illegal.
Pope Francis has been welcomed to Dublin by pro-LGBT demonstrators during his visit to Ireland.
Lisa Breslin, an Irish activist who started a campaign called "Say Nope to the Pope", told NPR, "We're at a crucial time in Ireland".
"Wounds are still open and there is much to be done to bring about justice and truth and healing for victims and survivors".
Organisers had expected more than 100,000 people to throng the streets of the Irish capital to greet the Pope's motorcade, but the initial welcome was muted.
The pontiff's arrival at Dublin airport on Saturday comes amid declining religious observance in the traditionally Catholic country and anger over the Catholic Church's record on tackling sexual abuse by priests.
Francis also mentioned the past remarks of his predecessor, Pope Benedict XVI, who in a 2010 pastoral letter of apology to Irish Catholics "spared no words in recognizing both the gravity of the situation and in demanding that "truly evangelical, just and effective" measures be taken in response to this betrayal of trust".
The Pope heard Mr Varadkar, a gay man, speak out against the traditional Catholic teaching on the family.
He will visit a homeless centre, before attending this evening's Feast of Families event at Croke Park stadium.
The pontiff will travel to County Mayo on Sunday morning for a visit to Knock Shrine, before returning to Dublin to close the World Meeting of Families at an afternoon Mass in front of an estimated 500,000 people in Phoenix Park.
As such, Williams, 36, still is on course to face a top-16 seed in the third round in her first Open as a mother. If the sisters do play each other, the victor might face world number one Simona Halep in the fourth round.
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This is what we've been waiting for here - the best fighting the best". "It's no secret that we needed to get in the rounds". But it is very awkward as they do not know where to look. "It is one thing that Tyson Fury has never had", he said.
I would now like to present the nominees for the video of the year. "How Madonna making this about her ", one Twitter user said. Eventually, Madonna tried to connect the dots of her story and Franklin's unparalleled legacy.
The stunning announcement sent Tesla's stock on a wild ride, prompting lawsuits and reportedly drawing scrutiny from regulators. Elson said most of the company's directors have relationships with Musk, who owns about 20 percent of the company.
Rahimi said that after Afghan security forces freed 149, the insurgents were still holding 21 hostages from the buses. It would only cover the Taliban, not other groups including Islamic State, officials said.
This Topic is Missing Your Voice. . #Redskins are signing RB Adrian Peterson , sources tell me and @RapSheet . He had just 81 yards in four games with the Saints before being traded to Arizona in October.
Since the World Cup started, he has had 14 shots on target come his way and he has conceded a worrying 10 goals. He had to get Maguire and Alderweireld because they wouldn't have made those mistakes at Brighton.
The 75-year-old Mnangagwa, a former enforcer for Mugabe, took power after Mugabe stepped down in November under military pressure. A Reuters witness said Harare was calm immediately after the ruling, with people going about their usual business.
American Republican Senator John McCain , the Vietnam war hero turned senator and presidential candidate, has died aged 81. After transient early years spent mostly at military bases, he graduated in 1954 from a Virginia boarding school.
Giuliani Tries To Clean Up 'Truth Isn't Truth' Comment
Anyone who thinks Rudy's " Truth isn't truth " is a gaff or misstatement isn't paying attention to the Trump defense strategy. It was Giuliani's practical deployment of the idea that truth is subjective, though, that was probably more meaningful.