Fr Hugh O'Flaherty disguised himself from the Nazi secret police and set up safe houses for thousands of soldiers in Rome between 1943-44 including one right next to the secret police's main headquarters in Rome.
His abilities to evade Nazi detection earned him the nickname the Vatican's Scarlet Pimpernel - a reference to a book character of the same name who rescued aristocrats in France who were being murdered before the French Revolution.
He was made a Commander of the British Empire (CBE) after World War II ended in 1945 and died in 1963 aged 65.
As part of festivities surrounding the plaque unveiling (below), members of Hugh O'Flaherty's family and the Hugh O'Flahery Memoral Society attended a special mass in the German College - the pontifical college where the plaque was unveiled - and Pope Francis' weekly Angelus (general audience) where he specifically mentioned the priest's work.
They were also given a tour of the notable sites where Fr O'Flaherty conducted his work while in Rome.
