The ceremony will be presided over by Cardinal Marcello Semeraro, prefect of the Vatican's Dicastery for the Causes of Saints.
The nine priests—Jan Świerc, Ignacy Antonowicz, Ignacy Dobiasz, Karol Golda, Franciszek Harazim, Ludwik Mroczek, Włodzimierz Szembek, Kazimierz Wojciechowski and Franciszek Miśka—died in the Nazi German concentration camps of Auschwitz and Dachau in 1941 and 1942 during World War II.
The Vatican recognised them as martyrs who were killed in odium fidei—out of hatred for the faith.
In the Roman Catholic Church, beatification is one step short of sainthood.
According to Poland's Catholic bishops, the beatification is a public recognition of the Salesians' witness to their faith.
"Remaining faithful to Christ, the Church and their Salesian vocation until the very end, the martyrs gave testimony that faith is not merely an idea, but a choice requiring courage and fidelity, especially in times of trial," the Polish Bishops' Conference said in a statement.
Historians estimate that nearly 1,800 of the roughly 3,000 clergy imprisoned at Dachau were from Poland, and 868 of them died there. Most of the at least 464 Catholic clergymen imprisoned at Auschwitz were also Polish.
Salesians are members of the Society of St. Francis de Sales, a Roman Catholic religious order founded by Italian priest John Bosco.
(mk/gs)