All 19 were recognised as martyrs in January, paving the way for Saturday’s ceremony in the Algerian city of Oran.
May "Monsignor Pierre Claverie... and his 18 companions, faithful messengers of the Gospel, humble artisans of peace... from now on be called blessed," said papal envoy Cardinal Angelo Becciu, reading the decree of beatification, the first step on the path to Roman Catholic sainthood.
Claverie, 58, was killed with his driver on August 1, 1996 when a remote-controlled bomb exploded at his residence in Oran.
He was among 19 clergy to be beatified, after their murders in a series of grisly atrocities between 1994 and 1996.
The ceremony was held under tight security at the esplanade of the Chapel of our Lady of Santa Cruz overlooking the Mediterranean city.
Officials, dignitaries and religious leaders attend Saturdays Mass at the Notre Dame de Santa Cruz basilica as part of a beatification ceremony, in Oran. Source: AAP
Some 1,200 people attended the ceremony, including pilgrims, relatives and friends of the beatified, many of whom came from abroad.
Opening the ceremony, Archbishop Paul Desfarges of Algiers paid tribute to "the thousands and thousands of victims of the Algerian civil war", describing them as anonymous heroes.
A minute of silence was then observed.
Algeria's 1991-2002 war between government forces and Islamists left up to 200,000 people dead.
Cardinal Angelo Becciu celebrates Saturdays Mass at the Notre Dame de Santa Cruz basilica as the popes special envoy. Source: AAP
In a message read during the ceremony by Becciu, Pope Francis spoke of his hope that "this celebration helps to heal the wounds of the past and create a new dynamic of meeting and living together".
The 19 clergy were declared martyrs by the Vatican in January 2018, since they were slain "in odium fidei", or out of hatred for the faith.
Pope Francis himself spoke of the beatification in prayers at Saint Peter's Square in the Vatican on Saturday.
On 26 March 1996, seven monks of the Trappist order from the Atlas Abbey of Tibhirine near Medea, Algeria were kidnapped during the Algerian Civil War. Source: AAP
"May this beatification be an incentive for all to build a world of fraternity and solidarity together", the pope said.
