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 was killed along with his driver in 1996 when a remote-controlled bomb exploded at his residence in Oran.
Seven French monks, abducted from the Priory of Our Lady of Atlas in Tibhirine, southwest of Algiers, by gunmen in March 1996 , were also beatified.
The ceremony was held under tight security at the Santa Cruz church overlooking Oran.
Some 1,200 people attended, including pilgrims, relatives and friends of the beatified, and many imams.
In the opening address, Archbishop Paul Desfarges of Algiers paid tribute to "the thousands and thousands of victims of the Algerian civil war", describing them as anonymous heroes.
Jean-Paul Vesco, Bishop of Oran, told RFI that organising such a ceremony was delicate.
“The risk is that in Algeria, and the Muslim world, people say ‘here’s a [Catholic] church making a fuss over 19 victims whereas we had 200,000 dead including a hundred imams. This isn’t even talked about in France.”
Vesco cited an Imam from the mosque near Oran's casbah who denounced the murder of two clerics during Friday prayers and was then killed himself.
If holding the beatification ceremony in Algeria means “we’re talking about all that, then it has meaning,” he concludes.
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.
"May this beatification be an incentive for all to build a world of fraternity and solidarity together", the pope said.