Former camp prisoners, local residents and government officials gathered on Tuesday at the site on the outskirts of the eastern city of Lublin to lay flowers and light candles in front of the mausoleum holding the ashes of the victims, according to media reports.
Majdanek, also known as Konzentrationslager Lublin, operated from October 1941 until July 22, 1944.
More than 130,000 people are believed to have passed through the camp. Victims perished from starvation, disease, forced labour, executions and in gas chambers.
In the final days before the camp's liberation by advancing Soviet forces, SS guards attempted to destroy evidence of their crimes, historians say.
They burned or buried camp records and set fire to the crematorium, where hundreds of prisoners transferred from a Gestapo prison in Lublin had been executed the day before.
Although the building was partially destroyed, key elements such as cremation ovens, a dissection table and metal urns used to store ashes survived the fire.
The gas chambers were left intact, preserving crucial evidence of the genocide carried out at the camp, Polish state news agency PAP reported.
In November 1944, just months after the camp's liberation, Polish authorities established a memorial museum on the grounds of the former camp, one of the earliest sites of Holocaust remembrance in postwar Europe.
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Source: IAR, PAP