Irena Sendler was a Polish Catholic social worker who served the Polish Underground and Żegota resistance in Nazi-occupied Warsaw. During her visits to the Warsaw Ghetto, ostensibly to survey Jews stricken by typhus for the Germans, she risked her life to smuggle thousands of Jewish children to safety. Babies and children were hidden in ambulances and disguised as packages, and she and her cohorts kept lists of their names in buried jars, which were hoped to assist in finding their families once the war was over.
Sendler was captured by the Nazis, tortured and sentenced to death for her acts of heroism, but was aided by Żegota and was able to escape and remain in hiding. After the war, she did her best to help reunite the Jewish children she had saved with their relatives, but sadly most of their parents had been executed in Treblinka or were never found.
Sendler's support for the Polish government-in-exile brought persecution by the Soviet-backed communist Polish state. However, she lived a long life and was eventually recognized internationally for her efforts.
Read more about Irena Sender at Wikipedia.