Francis, 88, celebrated a New Year's Day Mass in St Peter's Basilica on Wednesday that was dedicated to Mary, the mother of Jesus.
In his homily, he prayed that everyone learns to care for "every child born of a woman" and to protect "the precious gift of life: life in the womb, the lives of children, the lives of the suffering, the poor, the elderly, the lonely and the dying".
"I ask for a firm commitment to respect the dignity of human life from conception to natural death, so that each person may cherish his or her own life and all may look with hope to the future," he said, using the terminology of the church's opposition to abortion and euthanasia.
In recent years, the Argentine Jesuit has been speaking out more emphatically about abortion than he did at the start of his pontificate.
After two doctrinaire popes, Francis complained in the first months of his papacy in 2013 that the church had become obsessed by "small-minded rules" about hot-button issues like abortion.
Francis now regularly refers to procuring an abortion as "hiring a hitman to solve a problem".
He recently sparked outrage among some in Belgium when he criticised its abortion law as "homicidal" and announced he wanted to beatify Belgium's late king who abdicated for a day rather than approve legislation legalising the procedure.
The Vatican recently announced that the beatification process is under way for King Baudouin, who died in 1993.
The morning Mass marked the final big event of Francis' busy Christmas schedule.
For the pontiff, who suffers from recurrent respiratory problems, the season was even more challenging with the start of the Vatican's big Holy Year, a once-every-quarter-century celebration of the faith that is expected to bring 32 million pilgrims to Rome during 2025.
Speaking to pilgrims who gathered in a sun-filled St Peter's Square, Francis recalled the Jubilee's central message of the need to forgive debts.
He again called for world leaders from wealthy countries to eliminate or reduce the debts owed by poorer countries.
Francis urged Christian leaders in particular "to provide a good example" by taking the lead to forgive debts.
