A sombre procession was led by Anna Hackl, who lived close to the camp -- some 160 kilometres (100 miles) north-west of Vienna -- and risked her life to shelter two escaped prisoners.
Organisers said they wanted to pay tribute this year "to those who, at the risk of their own lives, stood by the victims of Nazi persecution."
Some 200,000 people from 40 nations -- around a quarter of them Jewish, but also Soviet civilians and 7,000 Republican Spaniards -- were incarcerated between 1938 and 1945 at Mauthausen, set in rolling hills near the Danube river.
Around 90,000 died from starvation and disease -- or were shot by the guards, hanged, throttled, beaten to death or gassed.
The US army liberated the camp on 5-7 May.
Several European leaders and former prisoners last week attended a ceremony to mark the exact date of the liberation and inaugurate a new visitor centre.
Israel's Justice Minister Tzipi Livni, who accompanied her father-in-law, himself a survivor of Mauthausen, told the crowd that the lesson of the camp had to be "never again."