Pope Francis is due to pray at the former death camp of Auschwitz-Birkenau in what was Nazi-occupied Poland.
He will walk in silence around the concentration and extermination camp where 1.1 million people, mostly Jews, were killed during World War Two.
On the third day of his visit to Poland, the pontiff will also meet camp survivors and Poles who risked their lives to hide Jews from the Nazis.
He is in the country to mark 1,050 years since it adopted Christianity.
Francis will be the third Pope to walk through the main gate of Auschwitz, under its infamous inscription “Arbeit Macht Frei” – work sets you free.
But unlike his German and Polish predecessors, he does not plan to speak about the horrors that occurred there, Adam Easton in Poland reports.
Instead he will pray and walk in silent contemplation as he looks at the piles of children’s shoes and the hair shorn from camp inmates.
The Argentine Pope is on a five-day trip to Poland.
During a World Youth Day rally in the southern city of Krakow on Thursday, he urged compassion for migrants.
He told hundreds of thousands of people that “a merciful heart opens up to welcome refugees and migrants” – a statement that puts him at odds with Poland’s anti-immigrant right-wing government.