Regina Jonas was born in Berlin in 1902 to a poor Orthodox family, and trained at the city's Higher Institute for Jewish Studies, a leading center of liberal Jewish scholarship, where she completed the full rabbinical curriculum expected of any male candidate for ordination. Her final examination thesis, submitted in 1930 and titled Can a Woman Be a Rabbi?, worked through the relevant Talmudic and later halachic sources and concluded, against the assumption of every rabbinical authority before her, that nothing in Jewish law actually barred a woman from serving as rabbi, only custom and precedent did.
The Institute itself, despite accepting her thesis, would not take the further step of ordaining her, and Jonas worked for several years as a Jewish studies teacher and religious instructor while the question of her formal status remained unresolved. In 1935, as Nazi persecution of German Jews was already well advanced, the liberal rabbi Max Dienemann privately ordained her, making her the first woman in the recorded history of Judaism to hold rabbinical ordination. She went on to preach, teach and offer pastoral care across Berlin's Jewish community, including hospitals, old age homes and social welfare institutions, functioning fully as a rabbi even though most of the community's official bodies never fully recognized her title.