On the third day of his visit to France, Leo again waded into the end-of-life debate unfolding around the world.
The issue roiled French politics for years before lawmakers recently approved legislation allowing adults with incurable illnesses to receive lethal medication.
Leo also met on Sunday with seven survivors of clergy sexual abuse, to atone for the Catholic Church's failure to protect its youngest and most vulnerable members from predator priests.
Leo's visit to the once staunchly Catholic and officially secular France has been marked by huge crowds - 800,000 at Leo's Mass on Paris' iconic Place de la Concorde - and his messaging against abortion and assisted dying.
France's National Assembly in 2024 enshrined abortion as a constitutional right and recently gave final approval to its end-of-life bill.
On Sunday, the Pope celebrated Mass before some 150,000 people - many in wheelchairs - on the prairie next to Lourdes' main basilica.
He then visited a care centre for sick people, telling those who live in "terrible pain" that they have inherent dignity that no law or algorithm can "eliminate".
"On the contrary, it is precisely in the name of this inalienable dignity of the human person that we must reject the temptation to cause death under the guise of false compassion," he said.
"What is legal is not necessarily moral," Leo said to applause.
Catholic teaching holds that all human life must be protected and defended from conception until natural death, leading to its firm opposition to abortion, euthanasia and medically assisted dying.
Leo had specifically criticised a medical-aid-in-dying law that recently took effect in his home state of Illinois - the 13th US state with such a law.
Lourdes became a major pilgrimage destination after the Catholic Church officially recognised visions of the Virgin Mary reported here by a young girl in 1858.
The site draws millions of pilgrims each year, especially sick and disabled believers hoping for a cure from the famed spring water in the Lourdes grotto where the visions purportedly occurred.
As a result in Lourdes, where the church has recognised 72 "miraculous" cures as authentic, the question of respecting even the most frail, sick and vulnerable is particularly acute.
Lourdes has also become a place of healing for survivors of clergy sexual abuse, and it was chosen as the site for Leo's encounter with victims. Leo met with them in a group and one-on-one in an encounter that lasted nearly two hours.
The Pope "listened to their stories, the pain and suffering they had endured - sometimes, unfortunately, with the complicity or silence of those who could have helped them - and their suggestions for ensuring that this does not happen again," the Vatican said in a statement.
The French church has faced a brutal reckoning with its legacy of abuse. An independent report in 2021 estimated 330,000 children had been abused over 70 years by some 3000 priests and church workers.
